Programs & Examples On #Errorlevel

check if command was successful in a batch file

Goodness I had a hard time finding the answer to this... Here it is:

cd thisDoesntExist
if %errorlevel% == 0 (
  echo Oh, I guess it does
  echo Huh.

How to take input in an array + PYTHON?

If the number of elements in the array is not given, you can alternatively make use of list comprehension like:

str_arr = raw_input().split(' ') //will take in a string of numbers separated by a space
arr = [int(num) for num in str_arr]

Is there a way to get element by XPath using JavaScript in Selenium WebDriver?

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;

System.setProperty("", "path of your chrome exe");
        WebDriver driver = new ChromeDriver();


Positioning background image, adding padding

To add space before background image, one could define the 'width' of element which is using 'background-image' object. And then to define a pixel value in 'background-position' property to create space from left side.

For example, I'd a scenario where I got a navigation menu which had a bullet before link item and the bullet graphic were changeable if corrosponding link turns into an active state. Further, the active link also had a background-color to show, and this background-color had approximate 15px padding both on left and right side of link item (so on left, it includes bullet icon of link too).

While padding-right fulfill the purpose to have background-color stretched upto 15px more on right of link text. The padding-left only added to space between link text and bullet.

So I took the width of background-color object from PSD design (for ex. 82px) and added that to li element (in a class created to show active state) and then I set background-position value to 20px. Which resulted in bullet icon shifted inside from the left edge. And its provided me desired output of having left padding before bullet icon used as background image.

Please note, you may need to adjust your padding / margin values accordingly, which may used either for space between link items or for spacing between bullet icon and link text.

Inserting HTML elements with JavaScript

If you want to insert HTML code inside existing page's tag use Jnerator. This tool was created specially for this goal.

Instead of writing next code

    var htmlCode = '<ul class=\'menu-countries\'><li
        class=\'item\'><img src=\'au.png\'></img><span>Australia </span></li><li
        class=\'item\'><img src=\'br.png\'> </img><span>Brazil</span></li><li
        class=\'item\'> <img src=\'ca.png\'></img><span>Canada</span></li></ul>';
    var element = document.getElementById('myTag');
    element.innerHTML = htmlCode;

You can write more understandable structure

    var jtag = $j.ul({
        class: 'menu-countries',
        child: [
            ${ class: 'item', child: [
                $j.img({ src: 'au.png' }),
                $j.span({ child: 'Australia' })
            ${ class: 'item', child: [
                $j.img({ src: 'br.png' }),
                $j.span({ child: 'Brazil' })
            ${ class: 'item', child: [
                $j.img({ src: 'ca.png' }),
                $j.span({ child: 'Canada' })
    var htmlCode = jtag.html();
    var element = document.getElementById('myTag');
    element.innerHTML = htmlCode;

PHP get dropdown value and text

$animals = array('--Select Animal--', 'Cat', 'Dog', 'Cow');
$selected_key = $_POST['animal'];
$selected_val = $animals[$_POST['animal']];

Use your $animals list to generate your dropdown list; you now can get the key & the value of that key.

How to replace innerHTML of a div using jQuery?

There are already answers which give how to change Inner HTML of element.

But I would suggest, you should use some animation like Fade Out/ Fade In to change HTML which gives good effect of changed HTML rather instantly changing inner HTML.

Use animation to change Inner HTML

$('#regTitle').fadeOut(500, function() {
    $(this).html('Hello World!').fadeIn(500);

If you have many functions which need this, then you can call common function which changes inner Html.

function changeInnerHtml(elementPath, newText){
    $(elementPath).fadeOut(500, function() {

How to get the current location in Google Maps Android API v2?

Try This

public class MyLocationListener implements LocationListener


public void onLocationChanged(Location loc)



String Text = “My current location is: ” +

“Latitud = ” + loc.getLatitude() +

“Longitud = ” + loc.getLongitude();

Toast.makeText( getApplicationContext(),Text,   Toast.LENGTH_SHORT).show();





How many characters can a Java String have?

While you can in theory Integer.MAX_VALUE characters, the JVM is limited in the size of the array it can use.

public static void main(String... args) {
    for (int i = 0; i < 4; i++) {
        int len = Integer.MAX_VALUE - i;
        try {
            char[] ch = new char[len];
            System.out.println("len: " + len + " OK");
        } catch (Error e) {
            System.out.println("len: " + len + " " + e);

on Oracle Java 8 update 92 prints

len: 2147483647 java.lang.OutOfMemoryError: Requested array size exceeds VM limit
len: 2147483646 java.lang.OutOfMemoryError: Requested array size exceeds VM limit
len: 2147483645 OK
len: 2147483644 OK

Note: in Java 9, Strings will use byte[] which will mean that multi-byte characters will use more than one byte and reduce the maximum further. If you have all four byte code-points e.g. emojis, you will only get around 500 million characters

Maven: How to rename the war file for the project?

Lookup pom.xml > project tag > build tag.

I would like solution below.



Worked for me. ^^

How to use global variable in node.js?

Most people advise against using global variables. If you want the same logger class in different modules you can do this


  module.exports = new logger(customConfig);


  var logger = require('./logger');

If you do want a global variable you can do:

global.logger = new logger(customConfig);

Setting the classpath in java using Eclipse IDE

Just had the same issue, for those having the same one it may be that you put the library on the modulepath rather than the classpath while adding it to your project

avrdude: stk500v2_ReceiveMessage(): timeout

I was running this code from Arduino setup , got same error resolve after changing
serial port to COM13
GO TO Option
tool>> serial port>> COM132

How to set the part of the text view is clickable

The solutions provided are pretty decent. However, I generally use a more simple solution.

Here is a linkify utility function

 * Method is used to Linkify words in a TextView
 * @param textView TextView who's text you want to change
 * @param textToLink The text to turn into a link
 * @param url   The url you want to send the user to
fun linkify(textView: TextView, textToLink: String, url: String) {
    val pattern = Pattern.compile(textToLink)
    Linkify.addLinks(textView, pattern, url, { _, _, _ -> true })
    { _, _ -> "" }

Using this function is pretty simple. Here is an example

    // terms and privacy
    val tvTerms = findViewById<TextView>(
    val tvPrivacy = findViewById<TextView>(
    Utils.linkify(tvTerms, resources.getString(R.string.terms),
    Utils.linkify(tvPrivacy, resources.getString(R.string.privacy),

How to show form input fields based on select value?

Demo on JSFiddle

$(document).ready(function () {
    toggleFields(); // call this first so we start out with the correct visibility depending on the selected form values
    // this will call our toggleFields function every time the selection value of our other field changes
    $("#dbType").change(function () {

// this toggles the visibility of other server
function toggleFields() {
    if ($("#dbType").val() === "other")


    <p>Choose type</p>
        <select id="dbType" name="dbType">
          <option>Choose Database Type</option>
          <option value="oracle">Oracle</option>
          <option value="mssql">MS SQL</option>
          <option value="mysql">MySQL</option>
          <option value="other">Other</option>
    <div id="otherServer">
            <input type="text" name="server_name" />
            <input type="text" name="port_no" />
    <p align="center">
        <input type="submit" value="Submit!" />

MongoDB: How to find the exact version of installed MongoDB

From the Java API:

Document result = mongoDatabase.runCommand(new Document("buildInfo", 1));
String version = (String) result.get("version");
List<Integer> versionArray = (List<Integer>) result.get("versionArray");

Ignore .pyc files in git repository

i try to use the sentence of a prior post and don't work recursively, then read some help and get this line:

find . -name "*.pyc" -exec git rm -f "{}" \;

p.d. is necessary to add *.pyc in .gitignore file to maintain git clean

echo "*.pyc" >> .gitignore


Use of #pragma in C

Putting #pragma once at the top of your header file will ensure that it is only included once. Note that #pragma once is not standard C99, but supported by most modern compilers.

An alternative is to use include guards (e.g. #ifndef MY_FILE #define MY_FILE ... #endif /* MY_FILE */)

Get child Node of another Node, given node name

You should read it recursively, some time ago I had the same question and solve with this code:

public void proccessMenuNodeList(NodeList nl, JMenuBar menubar) {
    for (int i = 0; i < nl.getLength(); i++) {
        proccessMenuNode(nl.item(i), menubar);

public void proccessMenuNode(Node n, Container parent) {
    Element element = (Element) n;
    String type = element.getAttribute("type");
    String name = element.getAttribute("name");
    if (type.equals("menu")) {
        NodeList nl = element.getChildNodes();
        JMenu menu = new JMenu(name);

        for (int i = 0; i < nl.getLength(); i++)
            proccessMenuNode(nl.item(i), menu);

    } else if (type.equals("item")) {
        JMenuItem item = new JMenuItem(name);

Probably you can adapt it for your case.

How do I configure Apache 2 to run Perl CGI scripts?

If you have successfully installed Apache web server and Perl please follow the following steps to run cgi script using perl on ubuntu systems.

Before starting with CGI scripting it is necessary to configure apache server in such a way that it recognizes the CGI directory (where the cgi programs are saved) and allow for the execution of programs within that directory.

  1. In Ubuntu cgi-bin directory usually resides in path /usr/lib , if not present create the cgi-bin directory using the following command.cgi-bin should be in this path itself.

     mkdir /usr/lib/cgi-bin
  2. Issue the following command to check the permission status of the directory.

     ls -l /usr/lib | less

Check whether the permission looks as “drwxr-xr-x 2 root root 4096 2011-11-23 09:08 cgi- bin” if yes go to step 3.

If not issue the following command to ensure the appropriate permission for our cgi-bin directory.

     sudo chmod 755 /usr/lib/cgi-bin
     sudo chmod root.root /usr/lib/cgi-bin
  1. Give execution permission to cgi-bin directory

     sudo chmod 755 /usr/lib/cgi-bin

Thus your cgi-bin directory is ready to go. This is where you put all your cgi scripts for execution. Our next step is configure apache to recognize cgi-bin directory and allow execution of all programs in it as cgi scripts.

Configuring Apache to run CGI script using perl

  1. A directive need to be added in the configuration file of apache server so it knows the presence of CGI and the location of its directories. Initially go to location of configuration file of apache and open it with your favorite text editor

    cd /etc/apache2/sites-available/ 
    sudo gedit 000-default.conf
  2. Copy the below content to the file 000-default.conf between the line of codes “DocumentRoot /var/www/html/” and “ErrorLog $ {APACHE_LOG_DIR}/error.log”

    ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
    <Directory "/usr/lib/cgi-bin">
    AllowOverride None
    Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
    Require all granted

  3. Restart apache server with the following code

    sudo service apache2 restart
  4. Now we need to enable cgi module which is present in newer versions of ubuntu by default

    sudo a2enmod cgi.load
    sudo a2enmod cgid.load
  5. At this point we can reload the apache webserver so that it reads the configuration files again.

    sudo service apache2 reload

The configuration part of apache is over now let us check it with a sample cgi perl program.

Testing it out

  1. Go to the cgi-bin directory and create a cgi file with extension .pl

    cd /usr/lib/cgi-bin/
    sudo gedit
  2. Copy the following code on and save it.

    #!/usr/bin/perl -w
    print “Content-type: text/html\r\n\r\n”;
    print “CGI working perfectly!! \n”;
  3. Now give the execution permission.

    sudo chmod 755
  4. Now open that file in your web browser http://Localhost/cgi-bin/

  5. If you see the output “CGI working perfectly” you are ready to go.Now dump all your programs into the cgi-bin directory and start using them.

NB: Don't forget to give your new programs in cgi-bin, chmod 755 permissions so as to run it successfully without any internal server errors.

CSS selectors ul li a {...} vs ul > li > a {...}

ul>li selects all li that are a direct child of ul whereas ul li selects all li that are anywhere within (descending as deep as you like) a ul


  <li><span><a href='#'>Something</a></span></li>
  <li><a href='#'>or Other</a></li>

And CSS:

li a{ color: green; }
li>a{ color: red; }

The colour of Something will remain green but or Other will be red

Part 2, you should write the rule to be appropriate to the situation, I think the speed difference would be incredibly small, and probably overshadowed by the extra characters involved in writing more code, and definitely overshadowed by the time taken by the developer to think about it.

However, as a rule of thumb, the more specific you are with your rules, the faster the CSS engines can locate the DOM elements you want to apply it to, so I expect li>a is faster than li a as the DOM search can be cut short earlier. It also means that nested anchors are not styled with that rule, is that what you want? <~~ much more pertinent question.

Laravel Mail::send() sending to multiple to or bcc addresses

it works for me fine, if you a have string, then simply explode it first.

$emails = array();

Mail::send('emails.maintenance',$mail_params, function($message) use ($emails) {
    foreach ($emails as $email) {

    $message->subject('My Email');

How to convert Java String into byte[]?

The object your method decompressGZIP() needs is a byte[].

So the basic, technical answer to the question you have asked is:

byte[] b = string.getBytes();
byte[] b = string.getBytes(Charset.forName("UTF-8"));
byte[] b = string.getBytes(StandardCharsets.UTF_8); // Java 7+ only

However the problem you appear to be wrestling with is that this doesn't display very well. Calling toString() will just give you the default Object.toString() which is the class name + memory address. In your result [B@38ee9f13, the [B means byte[] and 38ee9f13 is the memory address, separated by an @.

For display purposes you can use:


But this will just display as a sequence of comma-separated integers, which may or may not be what you want.

To get a readable String back from a byte[], use:

String string = new String(byte[] bytes, Charset charset);

The reason the Charset version is favoured, is that all String objects in Java are stored internally as UTF-16. When converting to a byte[] you will get a different breakdown of bytes for the given glyphs of that String, depending upon the chosen charset.

How do I check if an index exists on a table field in MySQL?

SHOW KEYS FROM  tablename WHERE Key_name='unique key name'

you can find if there exists an unique key in the table

How do I get the title of the current active window using c#?

you can use process class it's very easy. use this namespace

using System.Diagnostics;

if you want to make a button to get active window.

private void button1_Click(object sender, EventArgs e)
       Process currentp = Process.GetCurrentProcess();
       TextBox1.Text = currentp.MainWindowTitle;  //this textbox will be filled with active window.

Excel VBA Check if directory exists error

This is the cleanest way... BY FAR:

Public Function IsDir(s) As Boolean
    IsDir = CreateObject("Scripting.FileSystemObject").FolderExists(s)
End Function

How to use conditional breakpoint in Eclipse?

Make a normal breakpoint on the doIt(tablist[i]); line

Right-click -> Properties

Check 'Conditional'

Enter tablist[i].equalsIgnoreCase("LEADDELEGATES")

prevent refresh of page when button inside form clicked


<form onsubmit="return false;" id="myForm">


$('#myForm').submit(function() {

How do you initialise a dynamic array in C++?

You can't do it in one line easily. You can do:

char* c = new char[length];
memset(c, 0, length);

Or, you can overload the new operator:

void *operator new(size_t size, bool nullify)
    void *buf = malloc(size);

    if (!buf) {
             // Handle this

    memset(buf, '\0', size);

    return buf;

Then you will be able to do:

char* c = new(true) char[length];


char* c = new char[length];

will maintain the old behavior. (Note, if you want all news to zero out what they create, you can do it by using the same above but taking out the bool nullify part).

Do note that if you choose the second path you should overload the standard new operator (the one without the bool) and the delete operator too. This is because here you're using malloc(), and the standard says that malloc() + delete operations are undefined. So you have to overload delete to use free(), and the normal new to use malloc().

In practice though all implementations use malloc()/free() themselves internally, so even if you don't do it most likely you won't run into any problems (except language lawyers yelling at you)

Apache and Node.js on the Same Server

I recently ran into this kinda issue, where I need to communicate between client and server using websocket in a PHP based codeigniter project.

I resolved this issue by adding my port(node app running on) into Allow incoming TCP ports & Allow outgoing TCP ports lists.

You can find these configurations in Firewall Configurations in your server's WHM panel.

Buiding Hadoop with Eclipse / Maven - Missing artifact

I use below in my MR project.


Using sed, how do you print the first 'N' characters of a line?

don't have to use grep either

an example:

sed -n '/searchwords/{s/^\(.\{12\}\).*/\1/g;p}' file

How to insert blank lines in PDF?

directly use


to add an empty line.

How to get hostname from IP (Linux)?

In order to use nslookup, host or gethostbyname() then the target's name will need to be registered with DNS or statically defined in the hosts file on the machine running your program. Yes, you could connect to the target with SSH or some other application and query it directly, but for a generic solution you'll need some sort of DNS entry for it.

How to unset (remove) a collection element after fetching it?

I'm not fine with solutions that iterates over a collection and inside the loop manipulating the content of even that collection. This can result in unexpected behaviour.

See also here: and in a comment the given link

So, when using foreach if seems to be OK but IMHO the much more readable and simple solution is to filter your collection to a new one.

 * Filter all `selected` items
 * @link
$selected = $collection->filter(function($value, $key) {
    return $value->selected;

How to set textColor of UILabel in Swift

The easiest workaround is create dummy labels in IB, give them the text the color you like and set to hidden. You can then reference this color in your code to set your label to the desired color.

yourLabel.textColor = hiddenLabel.textColor

The only way I could change the text color programmatically was by using the standard colors, UIColor.white,

How to ignore SSL certificate errors in Apache HttpClient 4.0

a full working version for Apache HttpClient 4.1.3 (based on oleg's code above, but it still needed an allow_all_hostname_verifier on my system):

private static HttpClient trustEveryoneSslHttpClient() {
    try {
        SchemeRegistry registry = new SchemeRegistry();

        SSLSocketFactory socketFactory = new SSLSocketFactory(new TrustStrategy() {

            public boolean isTrusted(final X509Certificate[] chain, String authType) throws CertificateException {
                // Oh, I am easy...
                return true;

        }, org.apache.http.conn.ssl.SSLSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER);

        registry.register(new Scheme("https", 443, socketFactory));
        ThreadSafeClientConnManager mgr = new ThreadSafeClientConnManager(registry);
        DefaultHttpClient client = new DefaultHttpClient(mgr, new DefaultHttpClient().getParams());
        return client;
    } catch (GeneralSecurityException e) {
        throw new RuntimeException(e);

Note I'm re-throwing all exceptions because really, there's not much I can do if any of this fails in a real system!

python dictionary sorting in descending order based on values

Whenever one has a dictionary where the values are integers, the Counter data structure is often a better choice to represent the data than a dictionary.

If you already have a dictionary, a counter can easily be formed by:

c = Counter(d['123'])

as an example from your data.

The most_common function allows easy access to descending order of the items in the counter

The more complete writeup on the Counter data structure is at

Why am I getting a NoClassDefFoundError in Java?

NoClassDefFoundError In Java


  1. Java Virtual Machine is not able to find a particular class at runtime which was available at compile time.

  2. If a class was present during compile time but not available in java classpath during runtime.

enter image description here


  1. The class is not in Classpath, there is no sure shot way of knowing it but many times you can just have a look to print System.getproperty("java.classpath") and it will print the classpath from there you can at least get an idea of your actual runtime classpath.
  2. A simple example of NoClassDefFoundError is class belongs to a missing JAR file or JAR was not added into classpath or sometimes jar's name has been changed by someone like in my case one of my colleagues has changed tibco.jar into tibco_v3.jar and the program is failing with java.lang.NoClassDefFoundError and I were wondering what's wrong.

  3. Just try to run with explicitly -classpath option with the classpath you think will work and if it's working then it's a sure short sign that someone is overriding java classpath.

  4. Permission issue on JAR file can also cause NoClassDefFoundError in Java.
  5. Typo on XML Configuration can also cause NoClassDefFoundError in Java.
  6. when your compiled class which is defined in a package, doesn’t present in the same package while loading like in the case of JApplet it will throw NoClassDefFoundError in Java.

Possible Solutions:

  1. The class is not available in Java Classpath.
  2. If you are working in J2EE environment than the visibility of Class among multiple Classloader can also cause java.lang.NoClassDefFoundError, see examples and scenario section for detailed discussion.
  3. Check for java.lang.ExceptionInInitializerError in your log file. NoClassDefFoundError due to the failure of static initialization is quite common.
  4. Because NoClassDefFoundError is a subclass of java.lang.LinkageError it can also come if one of it dependency like native library may not available.
  5. Any start-up script is overriding Classpath environment variable.
  6. You might be running your program using jar command and class was not defined in manifest file's ClassPath attribute.


3 ways to solve NoClassDefFoundError

java.lang.NoClassDefFoundError Problem patterns

hasOwnProperty in JavaScript

Try this:

function welcomeMessage()
    var shape1 = new Shape();

When working with reflection in JavaScript, member objects are always refered to as the name as a string. For example:

for(i in obj) { ... }

The loop iterator i will be hold a string value with the name of the property. To use that in code you have to address the property using the array operator like this:

 for(i in obj) {
   alert("The value of obj." + i + " = " + obj[i]);

What are .a and .so files?

Wikipedia is a decent source for this info.

To learn about static library files like .a read Static libarary

To learn about shared library files like .so read Library_(computing)#Shared_libraries On this page, there is also useful info in the File naming section.

Find size of Git repository

I think this gives you the total list of all files in the repo history:

git rev-list --objects --all | git cat-file --batch-check="%(objectsize) %(rest)" | cut -d" " -f1 | paste -s -d + - | bc

You can replace --all with a treeish (HEAD, origin/master, etc.) to calculate the size of a branch.

How to define a Sql Server connection string to use in VB.NET?

Use the following Imports

Imports System.Data.SqlClient
Imports System.Data.Sql

Public SQLConn As New SqlConnection With {.ConnectionString = "Server=Desktop1[enter image description here][1];Database=Infostudio; Trusted_Connection=true;"}

Full string: enter image description here

How to source virtualenv activate in a Bash script

You should use multiple commands in one line. for example:

os.system(". Projects/virenv/bin/activate && python Projects/virenv/django-project/ runserver")

when you activate your virtual environment in one line, I think it forgets for other command lines and you can prevent this by using multiple commands in one line. It worked for me :)

onMeasure custom view explanation

If you don't need to change something onMeasure - there's absolutely no need for you to override it.

Devunwired code (the selected and most voted answer here) is almost identical to what the SDK implementation already does for you (and I checked - it had done that since 2009).

You can check the onMeasure method here :

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),
            getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));

public static int getDefaultSize(int size, int measureSpec) {
    int result = size;
    int specMode = MeasureSpec.getMode(measureSpec);
    int specSize = MeasureSpec.getSize(measureSpec);

    switch (specMode) {
    case MeasureSpec.UNSPECIFIED:
        result = size;
    case MeasureSpec.AT_MOST:
    case MeasureSpec.EXACTLY:
        result = specSize;
    return result;

Overriding SDK code to be replaced with the exact same code makes no sense.

This official doc's piece that claims "the default onMeasure() will always set a size of 100x100" - is wrong.

Cannot set content-type to 'application/json' in jQuery.ajax

If you use this:

contentType: "application/json"

AJAX won't sent GET or POST params to the server.... dont know why.

It took me hours to lear it today.

Just Use:

  { url : '',
    data : myFormData, type : 'POST', dataType : 'json', 
    // contentType: "application/json", 
    success : function(wsQuery) { }

Android WebView progress bar

I have just found a really good example of how to do this here: . You just need to change the setprogress from:

activity.setProgress(progress * 1000);


activity.setProgress(progress * 100);

How do I get HTTP Request body content in Laravel?

I don't think you want the data from your Request, I think you want the data from your Response. The two are different. Also you should build your response correctly in your controller.

Looking at the class in edit #2, I would make it look like this:

class XmlController extends Controller
    public function index()
        $content = Request::all();
        return Response::json($content);

Once you've gotten that far you should check the content of your response in your test case (use print_r if necessary), you should see the data inside.

More information on Laravel responses here:

Cannot redeclare function php

Remove the function and check the output of:


In which case, change the name of the function.

If you get false, you're including the file with that function twice, replace :




And replace :




EDIT : I'm just a little too late, post before beat me to it !

Can we have multiple <tbody> in same <table>?

I have created a JSFiddle where I have two nested ng-repeats with tables, and the parent ng-repeat on tbody. If you inspect any row in the table, you will see there are six tbody elements, i.e. the parent level.


        <table class="table table-hover table-condensed table-striped">
                    <th>Store ID</th>
                    <th>Employees H-sum</th>
            <tbody data-ng-repeat="storedata in storeDataModel.storedata">
                <tr id="" class="clickableRow" title="Click to toggle collapse/expand day summaries for this store." data-ng-click="selectTableRow($index,">
                <tr data-ng-show="dayDataCollapse[$index]">
                    <td colspan="2">&nbsp;</td>
                    <td colspan="7">
                            <div class="pull-right">
                                <table class="table table-hover table-condensed table-striped">
                                            <th>Date [YYYY-MM-dd]</th>
                                            <th>Employees H-sum</th>
                                        <tr data-ng-repeat="dayData in storeDataModel.storedata[$index].data.dayData">
                                            <td class="pullright">
                                                <button type="btn btn-small" title="Click to show transactions for this specific day..." data-ng-click=""><i class="icon-list"></i>

( Side note: This fills up the DOM if you have a lot of data on both levels, so I am therefore working on a directive to fetch data and replace, i.e. adding into DOM when clicking parent and removing when another is clicked or same parent again. To get the kind of behavior you find on, if you scroll down to the computers listed and click on the row (not the links). If you do that and inspect elements you will see that a tr is added and then removed if parent is clicked again or another. )

window.location.href not working

Please check you are using // not \\ by-mistake , like below



Oracle SqlDeveloper JDK path

I cannot believe Oracle's documentation is SO LAME! In some documents it is misleading people to point to the JDK by specifying the path to the JDK root, e.g. on a Mac:


Reviewing /Applications/ revealed the method they use to set up the path:

TMP_PATH=/usr/libexec/java_home -F -v 9 if [ -z "$TMP_PATH" ] ; then TMP_PATH=/usr/libexec/java_home -F -v 1.8 if [ -z "$TMP_PATH" ] ; then osascript -e 'tell app "System Events" to display dialog "SQL Developer requires a minimum of Java 8. \nJava 8 can be downloaded from:\n"' exit 1 fi fi

Executing this manually from Terminal:

/usr/libexec/java_home -F -v 1.8

Lists the path as:


And this is what you need to specify as the value for

SetJavaHome /Library/Java/JavaVirtualMachines/jdk1.8.0_152.jdk/Contents/Home

Thank you Oracle for wasting half a day on your "product" that does NOT even support your latest Java version, also released by you.

Environ Function code samples for VBA

Environ() gets you the value of any environment variable. These can be found by doing the following command in the Command Prompt:


If you wanted to get the username, you would do:


If you wanted to get the fully qualified name, you would do:

Environ("userdomain") & "\" & Environ("username")


How to show grep result with complete path or file name

It is similar to BVB Media's answer.

grep -rnw 'blablabla' `pwd`

It works fine on my ubuntu bash.

How can I use modulo operator (%) in JavaScript?

That would be the modulo operator, which produces the remainder of the division of two numbers.

Using PropertyInfo.GetValue()

In your example propertyInfo.GetValue(this, null) should work. Consider altering GetNamesAndTypesAndValues() as follows:

public void GetNamesAndTypesAndValues()
  foreach (PropertyInfo propertyInfo in allClassProperties)
    Console.WriteLine("{0} [type = {1}] [value = {2}]",
      propertyInfo.GetValue(this, null));

Android Fatal signal 11 (SIGSEGV) at 0x636f7d89 (code=1). How can it be tracked down?

I've faced with SIGSEGV on Android 4.4.4 (Nexuses, Samsungs) And it turned out that fatal error was in parsing null String using DecimalFormat

 static DecimalFormat decimalFormat = new DecimalFormat("###,###.###");
 void someMethod(String value) {
    Number number = decimalFormat.parse(value);//value is null, SIGSEGV will happen`

On Android > 21 it was handled successfully with try/catch

Check, using jQuery, if an element is 'display:none' or block on click

another shortcut i personally prefer more than .is() or .length:

   // is visible
}else {
   // is hidden

Collision Detection between two images in Java

First, use the bounding boxes as described by Jonathan Holland to find if you may have a collision.

From the (multi-color) sprites, create black and white versions. You probably already have these if your sprites are transparent (i.e. there are places which are inside the bounding box but you can still see the background). These are "masks".

Use Image.getRGB() on the mask to get at the pixels. For each pixel which isn't transparent, set a bit in an integer array (playerArray and enemyArray below). The size of the array is height if width <= 32 pixels, (width+31)/32*height otherwise. The code below is for width <= 32.

If you have a collision of the bounding boxes, do this:

// Find the first line where the two sprites might overlap
int linePlayer, lineEnemy;
if (player.y <= enemy.y) {
    linePlayer = enemy.y - player.y;
    lineEnemy = 0;
} else {
    linePlayer = 0;
    lineEnemy = player.y - enemy.y;
int line = Math.max(linePlayer, lineEnemy);

// Get the shift between the two
x = player.x - enemy.x;
int maxLines = Math.max(player.height, enemy.height);
for ( line < maxLines; line ++) {
    // if width > 32, then you need a second loop here
    long playerMask = playerArray[linePlayer];
    long enemyMask = enemyArray[lineEnemy];
    // Reproduce the shift between the two sprites
    if (x < 0) playerMask << (-x);
    else enemyMask << x;
    // If the two masks have common bits, binary AND will return != 0
    if ((playerMask & enemyMask) != 0) {
        // Contact!


Links: JGame, Framework for Small Java Games

Segmentation Fault - C

s is an uninitialized pointer; you are writing to a random location in memory. This will invoke undefined behaviour.

You need to allocate some memory for s. Also, never use gets; there is no way to prevent it overflowing the memory you allocate. Use fgets instead.

How do I print to the debug output window in a Win32 app?

If you need to see the output of an existing program that extensively used printf w/o changing the code (or with minimal changes) you can redefine printf as follows and add it to the common header (stdafx.h).

int print_log(const char* format, ...)
    static char s_printf_buf[1024];
    va_list args;
    va_start(args, format);
    _vsnprintf(s_printf_buf, sizeof(s_printf_buf), format, args);
    return 0;

#define printf(format, ...) \
        print_log(format, __VA_ARGS__)

PHP form - on submit stay on same page

The best way to stay on the same page is to post to the same page:

<form method="post" action="<?=$_SERVER['PHP_SELF'];?>">

jQuery first child of "this"

If you want to apply a selector to the context provided by an existing jQuery set, try the find() function:


Jørn Schou-Rode noted that you probably only want to find the first direct descendant of the context element, hence the child selector (>). He also points out that you could just as well use the children() function, which is very similar to find() but only searches one level deep in the hierarchy (which is all you need...):


how to convert an RGB image to numpy array?

You can get numpy array of rgb image easily by using numpy and Image from PIL

import numpy as np
from PIL import Image
import matplotlib.pyplot as plt

im ='*image_name*') #These two lines
im_arr = np.array(im) #are all you need
plt.imshow(im_arr) #Just to verify that image array has been constructed properly

Preventing an image from being draggable or selectable without using JS

I created a div element which has the same size as the image and is positioned on top of the image. Then, the mouse events do not go to the image element.

Checking if an object is a given type in Swift

If you don't know that you will get an array of dictionaries or single dictionary in the response from server you need to check whether the result contains an array or not.
In my case always receiving an array of dictionaries except once. So, to handle that I used the below code for swift 3.

if let str = strDict["item"] as? Array<Any>

Here as? Array checks whether the obtained value is array (of dictionary items). In else case you can handle if it is single dictionary item which is not kept inside an array.

How to check if a stored procedure exists before creating it

Here is the script that I use. With it, I avoid unnecessarily dropping and recreating the stored procs.

    SELECT *
    FROM sys.objects
    WHERE object_id = OBJECT_ID(N'[dbo].[uspMyProcedure]')
  EXEC sp_executesql N'CREATE PROCEDURE [dbo].[uspMyProcedure] AS select 1'

ALTER PROCEDURE [dbo].[uspMyProcedure] 
    @variable1 INTEGER  
   -- Stored procedure logic

Creating random colour in Java?

Here is a method for getting a random color:

private static Random sRandom;

public static synchronized int randomColor() {
    if (sRandom == null) {
        sRandom = new Random();
    return 0xff000000 + 256 * 256 * sRandom.nextInt(256) + 256 * sRandom.nextInt(256)
            + sRandom.nextInt(256);


  • Get the integer representation which can be used with java.awt.Color or
  • Keep a static reference to Random.

Find the last element of an array while using a foreach loop in PHP

Here's another way you could do it:

$arr = range(1, 10);

$end = end($arr);

while( list($k, $v) = each($arr) )
    if( $n == $end )
        echo 'last!';
        echo sprintf('%s ', $v);

How to display errors for my MySQLi query?

Just simply add or die(mysqli_error($db)); at the end of your query, this will print the mysqli error.

 mysqli_query($db,"INSERT INTO stockdetails (`itemdescription`,`itemnumber`,`sellerid`,`purchasedate`,`otherinfo`,`numberofitems`,`isitdelivered`,`price`) VALUES ('$itemdescription','$itemnumber','$sellerid','$purchasedate','$otherinfo','$numberofitems','$numberofitemsused','$isitdelivered','$price')") or die(mysqli_error($db));

As a side note I'd say you are at risk of mysql injection, check here How can I prevent SQL injection in PHP?. You should really use prepared statements to avoid any risk.

Error In PHP5 ..Unable to load dynamic library

I had a similar problem, which led me here:

$ phpunit --version
PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/lib/php5/20131226/' - /usr/lib/php5/20131226/ cannot open shared object file: No such file or directory in Unknown on line 0
PHPUnit 5.7.17 by Sebastian Bergmann and contributors.

Unlike the above, installing the software did not resolve my problem because I already had it.

$ sudo apt-get install php5-uprofiler
Reading package lists... Done
Building dependency tree       
Reading state information... Done
php5-uprofiler is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 52 not upgraded.

I found my solution via : Debian Bug report logs

$ sudo vim /etc/php5/mods-available/uprofiler.ini

I edited the ini file, changing to .... the result, happily:

$ phpunit --version
PHPUnit 5.7.17 by Sebastian Bergmann and contributors.

i.e. no more warning.

Can Selenium WebDriver open browser windows silently in the background?

If you are using Ubuntu (Gnome), one simple workaround is to install Gnome extension auto-move-window:

Then set the browser (eg. Chrome) to another workspace (eg. Workspace 2). The browser will silently run in other workspace and not bother you anymore. You can still use Chrome in your workspace without any interruption.

How to install wget in macOS?

You need to do

./configure --with-ssl=openssl --with-libssl-prefix=/usr/local/ssl

Instead of this

./configure --with-ssl=openssl

A JOIN With Additional Conditions Using Query Builder or Eloquent

There's a difference between the raw queries and standard selects (between the DB::raw and DB::select methods).

You can do what you want using a DB::select and simply dropping in the ? placeholder much like you do with prepared statements (it's actually what it's doing).

A small example:

$results = DB::select('SELECT * FROM user WHERE username=?', ['jason']);

The second parameter is an array of values that will be used to replace the placeholders in the query from left to right.

Importing a long list of constants to a Python file

And ofcourse you can do:


from a import *

Setting selected values for ng-options bound select elements

You can use the ID field as the equality identifier. You can't use the adhoc object for this case because AngularJS checks references equality when comparing objects.

    ng-options="choice.ID as choice.Name for choice in Choice.Options">

AutoComplete TextBox in WPF

If you have a small number of values to auto complete, you can simply add them in xaml. Typing will invoke auto-complete, plus you have dropdowns too.

<ComboBox Text="{Binding CheckSeconds, UpdateSourceTrigger=PropertyChanged}"
    <ComboBoxItem Content="60"/>
    <ComboBoxItem Content="120"/>
    <ComboBoxItem Content="180"/>
    <ComboBoxItem Content="300"/>
    <ComboBoxItem Content="900"/>

Convert String to System.IO.Stream

System.IO.MemoryStream mStream = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes( contents));

Linq with group by having count

Below solution may help you.

var unmanagedDownloadcountwithfilter = from count in unmanagedDownloadCount.Where(d =>d.downloaddate >= startDate && d.downloaddate <= endDate)
group count by count.unmanagedassetregistryid into grouped
where grouped.Count() > request.Download
select new
   UnmanagedAssetRegistryID = grouped.Key,
   Count = grouped.Count()

Difference between abstract class and interface in Python

In a more basic way to explain: An interface is sort of like an empty muffin pan. It's a class file with a set of method definitions that have no code.

An abstract class is the same thing, but not all functions need to be empty. Some can have code. It's not strictly empty.

Why differentiate: There's not much practical difference in Python, but on the planning level for a large project, it could be more common to talk about interfaces, since there's no code. Especially if you're working with Java programmers who are accustomed to the term.

intellij incorrectly saying no beans of type found for autowired repository

simple you have to do 2 steps

  1. add hibernate-core dependency
  2. change @Autowired to @Resource.
==>> change @Autowired to  @Resource

Check if list<t> contains any of another list

You could use a nested Any() for this check which is available on any Enumerable:

bool hasMatch = myStrings.Any(x => parameters.Any(y => y.source == x));

Faster performing on larger collections would be to project parameters to source and then use Intersect which internally uses a HashSet<T> so instead of O(n^2) for the first approach (the equivalent of two nested loops) you can do the check in O(n) :

bool hasMatch = parameters.Select(x => x.source)

Also as a side comment you should capitalize your class names and property names to conform with the C# style guidelines.

link with target="_blank" does not open in new tab in Chrome

most simple answer

<a onclick=",'_blank');return false;" href="">Some Other Site</a>

it will work

Nginx Different Domains on Same IP

Your "listen" directives are wrong. See this page:

They should be

server {
    listen      80;
    root /var/www/domain1;

server {
    listen       80;
    root /var/www/domain2;

Note, I have only included the relevant lines. Everything else looked okay but I just deleted it for clarity. To test it you might want to try serving a text file from each server first before actually serving php. That's why I left the 'root' directive in there.

Printing PDFs from Windows Command Line

Looks like you are missing the printer name, driver, and port - in that order. Your final command should resemble:

AcroRd32.exe /t <file.pdf> <printer_name> <printer_driver> <printer_port>

For example:

"C:\Program Files (x86)\Adobe\Reader 11.0\Reader\AcroRd32.exe" /t "C:\Folder\File.pdf" "Brother MFC-7820N USB Printer" "Brother MFC-7820N USB Printer" "IP_192.168.10.110"

Note: To find the printer information, right click your printer and choose properties. In my case shown above, the printer name and driver name matched - but your information may differ.

Viewing local storage contents on IE

Since localStorage is a global object, you can add a watch in the dev tools. Just enter the dev tools, goto "watch", click on "Click to add..." and type in "localStorage".

Mouseover or hover vue.js

Please take a look at the vue-mouseover package if you are not satisfied how does this code look:

    @mouseover="isMouseover = true"
    @mouseleave="isMouseover = false"

vue-mouseover provides a v-mouseover directive that automaticaly updates the specified data context property when the cursor enters or leaves an HTML element the directive is attached to.

By default in the next example isMouseover property will be true when the cursor is over an HTML element and false otherwise:

<div v-mouseover="isMouseover" />

Also by default isMouseover will be initially assigned when v-mouseover is attached to the div element, so it will not remain unassigned before the first mouseenter/mouseleave event.

You can specify custom values via v-mouseover-value directive:



        mouseenter: customMouseenterValue,
        mouseleave: customMouseleaveValue

Custom default values can be passed to the package via options object during setup.

angular2 manually firing click event on particular element

If you want to imitate click on the DOM element like this:

<a (click)="showLogin($event)">login</a>

and have something like this on the page:

<li ngbDropdown>
    <a ngbDropdownToggle id="login-menu">

your function in component.ts should be like this:

showLogin(event) {

Get and Set Screen Resolution

in Winforms, there is a Screen class you can use to get data about screen dimensions and color depth for all displays connected to the computer. Here's the docs page:

CHANGING the screen resolution is trickier. There is a Resolution third party class that wraps the native code you'd otherwise hook into. Use its CResolution nested class to set the screen resolution to a new height and width; but understand that doing this will only work for height/width combinations the display actually supports (800x600, 1024x768, etc, not 817x435).

How to read GET data from a URL using JavaScript?

I think this should also work:

function $_GET(q,s) {
    s = (s) ? s :;
    var re = new RegExp('&amp;'+q+'=([^&amp;]*)','i');
    return (s=s.replace(/^\?/,'&amp;').match(re)) ?s=s[1] :s='';

Just call it like this:

var value = $_GET('myvariable');

Uncaught TypeError : cannot read property 'replace' of undefined In Grid

In my case, I was using a View that I´ve converted to partial view and I forgot to remove the template from "@section scripts". Removing the section block, solved my problem. This is because the sections aren´t rendered in partial views.

OS specific instructions in CMAKE: How to?

You have some special words from CMAKE, take a look:

    // do something for Linux
    // do something for other OS

How to use GROUP_CONCAT in a CONCAT in MySQL

IF OBJECT_ID('master..test') is not null Drop table test

INSERT INTO test VALUES (1, 'A', 4);
INSERT INTO test VALUES (1, 'A', 5);
INSERT INTO test VALUES (1, 'B', 8);
INSERT INTO test VALUES (2, 'C', 9);

select distinct NAME , LIST = Replace(Replace(Stuff((select ',', +Value from test where name = for xml path('')), 1,1,''),'<Value>', ''),'</Value>','') from test _a order by 1 desc

My table name is test , and for concatination I use the For XML Path('') syntax. The stuff function inserts a string into another string. It deletes a specified length of characters in the first string at the start position and then inserts the second string into the first string at the start position.

STUFF functions looks like this : STUFF (character_expression , start , length ,character_expression )

character_expression Is an expression of character data. character_expression can be a constant, variable, or column of either character or binary data.

start Is an integer value that specifies the location to start deletion and insertion. If start or length is negative, a null string is returned. If start is longer than the first character_expression, a null string is returned. start can be of type bigint.

length Is an integer that specifies the number of characters to delete. If length is longer than the first character_expression, deletion occurs up to the last character in the last character_expression. length can be of type bigint.

How do relative file paths work in Eclipse?

Paraphrasing from

The classes under resolve relative pathnames against the current user directory, which is typically the directory in which the virtual machine was started.

Eclipse sets the working directory to the top-level project folder.

Can anyone recommend a simple Java web-app framework?

Recently i found the AribaWeb Framework which looks very promising. It offers good functionality (even AJAX), good documentation. written in Groovy/Java and even includes a Tomcat-Server. Trying to get into Spring really made me mad.

How can I change the width and height of slides on Slick Carousel?

You could also use this:

   //other settings ................
   respondTo: 'slider', //makes the slider to change width depending on the container it is in
   adaptiveHeight: true //makes the height change depending on the height of the element inside

.NET: Simplest way to send POST with data and read response

Given other answers are a few years old, currently here are my thoughts that may be helpful:

Simplest way

private async Task<string> PostAsync(Uri uri, HttpContent dataOut)
    var client = new HttpClient();
    var response = await client.PostAsync(uri, dataOut);
    return await response.Content.ReadAsStringAsync();
    // For non strings you can use other Content.ReadAs...() method variations

A More Practical Example

Often we are dealing with known types and JSON, so you can further extend this idea with any number of implementations, such as:

public async Task<T> PostJsonAsync<T>(Uri uri, object dtoOut)
    var content = new StringContent(JsonConvert.SerializeObject(dtoOut));
    content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");

    var results = await PostAsync(uri, content); // from previous block of code

    return JsonConvert.DeserializeObject<T>(results); // using Newtonsoft.Json

An example of how this could be called:

var dataToSendOutToApi = new MyDtoOut();
var uri = new Uri("");
var dataFromApi = await PostJsonAsync<MyDtoIn>(uri, dataToSendOutToApi);

execute function after complete page load

call a function after complete page load set time out

setTimeout(function() {_x000D_
   var val = $('.GridStyle tr:nth-child(2) td:nth-child(4)').text();_x000D_
 for(var i, j = 0; i = ddl2.options[j]; j++) {_x000D_
  if(i.text == val) {      _x000D_
   ddl2.selectedIndex = i.index;_x000D_
 } _x000D_
}, 1000);

How to get a cookie from an AJAX response?

The browser cannot give access to 3rd party cookies like those received from ajax requests for security reasons, however it takes care of those automatically for you!

For this to work you need to:

1) login with the ajax request from which you expect cookies to be returned:

$.ajax("", {
     method: 'POST',
     data: {login_id: user, password: password},
     crossDomain: true,
     success: login_success,
     error: login_error

2) Connect with xhrFields: { withCredentials: true } in the next ajax request(s) to use the credentials saved by the browser

$.ajax("", {
     method: 'GET',
     xhrFields: { withCredentials: true },
     crossDomain: true,
     success: whatever_success,
     error: whatever_error

The browser takes care of these cookies for you even though they are not readable from the headers nor the document.cookie

How to store Configuration file and read it using React

If you used Create React App, you can set an environment variable using a .env file. The documentation is here:

Basically do something like this in the .env file at the project root.


Note that the variable name must start with REACT_APP_

You can access it from your component with


Query to convert from datetime to date mysql

Use the DATE function:

SELECT DATE(orders.date_purchased) AS date

python: restarting a loop

Changing the index variable i from within the loop is unlikely to do what you expect. You may need to use a while loop instead, and control the incrementing of the loop variable yourself. Each time around the for loop, i is reassigned with the next value from range(). So something like:

i = 2
while i < n:
        do something
        do something else
        i = 2 # restart the loop
    i += 1

In my example, the continue statement jumps back up to the top of the loop, skipping the i += 1 statement for that iteration. Otherwise, i is incremented as you would expect (same as the for loop).

In ASP.NET MVC: All possible ways to call Controller Action Method from a Razor View

Method 1 : Using jQuery Ajax Get call (partial page update).

Suitable for when you need to retrieve jSon data from database.

Controller's Action Method

public ActionResult Foo(string id)
    var person = Something.GetPersonByID(id);
    return Json(person, JsonRequestBehavior.AllowGet);

Jquery GET

function getPerson(id) {
        url: '@Url.Action("Foo", "SomeController")',
        type: 'GET',
        dataType: 'json',
        // we set cache: false because GET requests are often cached by browsers
        // IE is particularly aggressive in that respect
        cache: false,
        data: { id: id },
        success: function(person) {

Person class

public class Person
    public string FirstName { get; set; }
    public string LastName { get; set; }

Method 2 : Using jQuery Ajax Post call (partial page update).

Suitable for when you need to do partial page post data into database.

Post method is also same like above just replace [HttpPost] on Action method and type as post for jquery method.

For more information check Posting JSON Data to MVC Controllers Here

Method 3 : As a Form post scenario (full page update).

Suitable for when you need to save or update data into database.


@using (Html.BeginForm("SaveData","ControllerName", FormMethod.Post))
    @Html.TextBoxFor(model => m.Text)
    <input type="submit" value="Save" />

Action Method

public ActionResult SaveData(FormCollection form)
        // Get movie to update
        return View();

Method 4 : As a Form Get scenario (full page update).

Suitable for when you need to Get data from database

Get method also same like above just replace [HttpGet] on Action method and FormMethod.Get for View's form method.

I hope this will help to you.

How to compare each item in a list with the rest, only once?

Your solution is correct, but your outer loop is still longer than needed. You don't need to compare the last element with anything else because it's been already compared with all the others in the previous iterations. Your inner loop still prevents that, but since we're talking about collision detection you can save the unnecessary check.

Using the same language you used to illustrate your algorithm, you'd come with something like this:

for (int i = 0, i < mylist.size() - 1; ++i)
    for (int j = i + 1, j < mylist.size(); --j)
        compare(mylist[i], mylist[j])

TypeScript Objects as Dictionary types as in C#

In newer versions of typescript you can use:

type Customers = Record<string, Customer>

In older versions you can use:

var map: { [email: string]: Customer; } = { };
map['[email protected]'] = new Customer(); // OK
map[14] = new Customer(); // Not OK, 14 is not a string
map['[email protected]'] = 'x'; // Not OK, 'x' is not a customer

You can also make an interface if you don't want to type that whole type annotation out every time:

interface StringToCustomerMap {
    [email: string]: Customer;

var map: StringToCustomerMap = { };
// Equivalent to first line of above

Unable to negotiate with XX.XXX.XX.XX: no matching host key type found. Their offer: ssh-dss

For me this worked: (added into .ssh\config)

Host *
HostkeyAlgorithms +ssh-dss
PubkeyAcceptedKeyTypes +ssh-dss

PHP using Gettext inside <<<EOF string

As far as I can see, you just added heredoc by mistake
No need to use ugly heredoc syntax here.
Just remove it and everything will work:

<p><?= _("World"); ?></p>

SQLite equivalent to ISNULL(), NVL(), IFNULL() or COALESCE()

Try this



select ifnull(InfoDetail,'') InfoDetail; -- this will replace null with ''
select ifnull(NULL,'THIS IS NULL');-- More clearly....

The ifnull() function returns a copy of its first non-NULL argument, or NULL if both arguments are NULL. Ifnull() must have exactly 2 arguments. The ifnull() function is equivalent to coalesce() with two arguments.

What is the difference between a candidate key and a primary key?

A primary key is a column (or columns) in a table that uniquely identifies the rows in that table.


CustomerNo  FirstName   LastName
1   Sally   Thompson
2   Sally   Henderson
3   Harry   Henderson
4   Sandra  Wellington

For example, in the table above, CustomerNo is the primary key.

The values placed in primary key columns must be unique for each row: no duplicates can be tolerated. In addition, nulls are not allowed in primary key columns.

So, having told you that it is possible to use one or more columns as a primary key, how do you decide which columns (and how many) to choose?

Well there are times when it is advisable or essential to use multiple columns. However, if you cannot see an immediate reason to use multiple columns, then use one. This isn't an absolute rule, it is simply advice. However, primary keys made up of single columns are generally easier to maintain and faster in operation. This means that if you query the database, you will usually get the answer back faster if the tables have single column primary keys.

Next question — which column should you pick? The easiest way to choose a column as a primary key (and a method that is reasonably commonly employed) is to get the database itself to automatically allocate a unique number to each row.

In a table of employees, clearly any column like FirstName is a poor choice since you cannot control employee's first names. Often there is only one choice for the primary key, as in the case above. However, if there is more than one, these can be described as 'candidate keys' — the name reflects that they are candidates for the responsible job of primary key.

How to set the "Content-Type ... charset" in the request header using a HTML link

This is not possible from HTML on. The closest what you can get is the accept-charset attribute of the <form>. Only MSIE browser adheres that, but even then it is doing it wrong (e.g. CP1252 is actually been used when it says that it has sent ISO-8859-1). Other browsers are fully ignoring it and they are using the charset as specified in the Content-Type header of the response. Setting the character encoding right is basically fully the responsiblity of the server side. The client side should just send it back in the same charset as the server has sent the response in.

To the point, you should really configure the character encoding stuff entirely from the server side on. To overcome the inability to edit URIEncoding attribute, someone here on SO wrote a (complex) filter: Detect the URI encoding automatically in Tomcat. You may find it useful as well (note: I haven't tested it).

Update: Noted should be that the meta tag as given in your question is ignored when the content is been transferred over HTTP. Instead, the HTTP response Content-Type header will be used to determine the content type and character encoding. You can determine the HTTP header with for example Firebug, in the Net panel.

alt text

What is apache's maximum url length?

The default limit for the length of the request line is 8190 bytes (see LimitRequestLine directive). And if we subtract three bytes for the request method (i.e. GET), eight bytes for the version information (i.e. HTTP/1.0/HTTP/1.1) and two bytes for the separating space, we end up with 8177 bytes for the URI path plus query.

AngularJS - convert dates in controller

All solutions here doesn't really bind the model to the input because you will have to change back the dateAsString to be saved as date in your object (in the controller after the form will be submitted).

If you don't need the binding effect, but just to show it in the input,

a simple could be:

<input type="date" value="{{ | date: 'yyyy-MM-dd' }}" id="item_date" />

Then, if you like, in the controller, you can save the edited date in this way:

  $ = new Date(document.getElementById('item_date').value).getTime();

be aware: in your controller, you have to declare your item variable as $scope.item in order for this to work.

How to get the id of the element clicked using jQuery

Since you are loading in the spans via ajax you will have to attach delegate handlers to the events to catch them as they bubble up.


you will want to attach the event to the closest static member you can to increase efficiency.


is better than binding to the document for instance.

This question may help you understand

Direct vs. Delegated - jQuery .on()

m2e lifecycle-mapping not found

Here's how I do it: I put m2e's lifecycle-mapping plugin in a separate profile instead of the default <build> section. the profile is auto-activated during eclipse builds by presence of a m2e property (instead of manual activation in settings.xml or otherwise). this will handle the m2e cases, while command-line maven will simply skip the profile and the m2e lifecycle-mapping plugin without any warnings, and everybody is happy.

      <!-- This profile is only active when the property "m2e.version"
        is set, which is the case when building in Eclipse with m2e. -->

                        <!-- either <ignore> XOR <execute>,
                          you must remove the other one. -->

                        <!-- execute: tells m2e to run the execution just like command-line maven.
                          from m2e's point of view, this is not recommended, because it is not
                          deterministic and may make your eclipse unresponsive or behave strangely. -->
                          <!-- runOnIncremental: tells m2e to run the plugin-execution
                            on each auto-build (true) or only on full-build (false). -->

                        <!-- ignore: tells m2eclipse to skip the execution. -->
                        <ignore />


Automatically plot different colored lines

Late answer, but two things to add:

  • For information on how to change the 'ColorOrder' property and how to set a global default with 'DefaultAxesColorOrder', see the "Appendix" at the bottom of this post.
  • There is a great tool on the MATLAB Central File Exchange to generate any number of visually distinct colors, if you have the Image Processing Toolbox to use it. Read on for details.

The ColorOrder axes property allows MATLAB to automatically cycle through a list of colors when using hold on/all (again, see Appendix below for how to set/get the ColorOrder for a specific axis or globally via DefaultAxesColorOrder). However, by default MATLAB only specifies a short list of colors (just 7 as of R2013b) to cycle through, and on the other hand it can be problematic to find a good set of colors for more data series. For 10 plots, you obviously cannot rely on the default ColorOrder.

A great way to define N visually distinct colors is with the "Generate Maximally Perceptually-Distinct Colors" (GMPDC) submission on the MATLAB Central File File Exchange. It is best described in the author's own words:

This function generates a set of colors which are distinguishable by reference to the "Lab" color space, which more closely matches human color perception than RGB. Given an initial large list of possible colors, it iteratively chooses the entry in the list that is farthest (in Lab space) from all previously-chosen entries.

For example, when 25 colors are requested:

25 "maximally perceptually-distinct colors"

The GMPDC submission was chosen on MathWorks' official blog as Pick of the Week in 2010 in part because of the ability to request an arbitrary number of colors (in contrast to MATLAB's built in 7 default colors). They even made the excellent suggestion to set MATLAB's ColorOrder on startup to,


Of course, you can set the ColorOrder for a single axis or simply generate a list of colors to use in any way you like. For example, to generate 10 "maximally perceptually-distinct colors" and use them for 10 plots on the same axis (but not using ColorOrder, thus requiring a loop):

% Starting with X of size N-by-P-by-2, where P is number of plots
mpdc10 = distinguishable_colors(10) % 10x3 color list
hold on
for ii=1:size(X,2),

The process is simplified, requiring no for loop, with the ColorOrder axis property:

% X of size N-by-P-by-2
mpdc10 = distinguishable_colors(10)
ha = axes; hold(ha,'on')
set(ha,'ColorOrder',mpdc10)    % --- set ColorOrder HERE ---
plot(X(:,:,1),X(:,:,2),'-.')   % loop NOT needed, 'Color' NOT needed. Yay!


To get the ColorOrder RGB array used for the current axis,


To get the default ColorOrder for new axes,


Example of setting new global ColorOrder with 10 colors on MATLAB start, in startup.m:


How to disable manual input for JQuery UI Datepicker field?

When you make the input, set it to be readonly.

<input type="text" name="datepicker" id="datepicker" readonly="readonly" />

gnuplot plotting multiple line graphs

andyras is completely correct. One minor addition, try this (for example)

plot 'ls.dat' using 4:xtic(1)

This will keep your datafile in the correct order, but also preserve your version tic labels on the x-axis.

How to detect DIV's dimension changed?

This is a really old question, but I figured I'd post my solution to this.

I tried to use ResizeSensor since everyone seemed to have a pretty big crush on it. After implementing though, I realized that under the hood the Element Query requires the element in question to have position relative or absolute applied to it, which didn't work for my situation.

I ended up handling this with an Rxjs interval instead of a straight setTimeout or requestAnimationFrame like previous implementations.

What's nice about the observable flavor of an interval is that you get to modify the stream however any other observable can be handled. For me, a basic implementation was enough, but you could go crazy and do all sorts of merges, etc.

In the below example, I'm tracking the inner (green) div's width changes. It has a width set to 50%, but a max-width of 200px. Dragging the slider affects the wrapper (gray) div's width. You can see that the observable only fires when the inner div's width changes, which only happens if the outer div's width is smaller than 400px.

const { interval } = rxjs;_x000D_
const { distinctUntilChanged, map, filter } = rxjs.operators;_x000D_
const wrapper = document.getElementById('my-wrapper');_x000D_
const input = document.getElementById('width-input');_x000D_
function subscribeToResize() {_x000D_
  const timer = interval(100);_x000D_
  const myDiv = document.getElementById('my-div');_x000D_
  const widthElement = document.getElementById('width');_x000D_
  const isMax = document.getElementById('is-max');_x000D_
    NOTE: This is the important bit here _x000D_
      map(() => myDiv ? Math.round(myDiv.getBoundingClientRect().width) : 0),_x000D_
      // adding a takeUntil(), here as well would allow cleanup when the component is destroyed_x000D_
      .subscribe((width) => {        _x000D_
        widthElement.innerHTML = width;_x000D_
        isMax.innerHTML = width === 200 ? 'Max width' : '50% width';_x000D_
function defineRange() {_x000D_
  input.min = 200;_x000D_
  input.max = window.innerWidth;_x000D_
  input.step = 10;_x000D_
  input.value = input.max - 50;_x000D_
function bindInputToWrapper() {_x000D_
  input.addEventListener('input', (event) => {_x000D_ = `${}px`;_x000D_
.inner {_x000D_
  width: 50%;_x000D_
  max-width: 200px;_x000D_
/* Aesthetic styles only */_x000D_
.inner {_x000D_
  background: #16a085;_x000D_
.wrapper {_x000D_
  background: #ecf0f1;_x000D_
  color: white;_x000D_
  margin-top: 24px;_x000D_
.content {_x000D_
  padding: 12px;_x000D_
body {_x000D_
  font-family: sans-serif;_x000D_
  font-weight: bold;_x000D_
<script src=""></script>_x000D_
<h1>Resize Browser width</h1>_x000D_
<label for="width-input">Adjust the width of the wrapper element</label>_x000D_
  <input type="range" id="width-input">_x000D_
<div id="my-wrapper" class="wrapper">_x000D_
  <div id="my-div" class="inner">_x000D_
    <div class="content">_x000D_
      Width: <span id="width"></span>px_x000D_
      <div id="is-max"></div>  _x000D_

How to use jQuery to get the current value of a file input field

I think it should be


Apache 2.4 - Request exceeded the limit of 10 internal redirects due to probable configuration error

You're getting into looping most likely due to these rules:

RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]

Just comment it out and try again in a new browser.

Angular ForEach in Angular4/Typescript?

arrayData.forEach((key : any, val: any) => {
                        key['index'] = val + 1;

                        arrayData2.forEach((keys : any, vals :any) => {
                            if (key.group_id == {
                                key.group_name = keys.group_name;

Importing lodash into angular2 + typescript application

Managing types via typings and tsd commands is ultimately deprecated in favor of using npm via npm install @types/lodash.

However, I struggled with "Cannot find module lodash" in import statement for a long time:

import * as _ from 'lodash';

Ultimately I realized Typescript will only load types from node_modules/@types start version 2, and my VsCode Language service was still using 1.8, so the editor was reporting errors.

If you're using VSCode you'll want to include

"typescript.tsdk":  "node_modules/typescript/lib"

in your VSCode settings.json file (for workspace settings) and make sure you have typescript version >= 2.0.0 installed via npm install [email protected] --save-dev

After that my editor wouldn't complain about the import statement.

Check element exists in array

Look before you leap (LBYL):

if idx < len(array):
    # handle this

Easier to ask forgiveness than permission (EAFP):

except IndexError:
    # handle this

In Python, EAFP seems to be the popular and preferred style. It is generally more reliable, and avoids an entire class of bugs (time of check vs. time of use). All other things being equal, the try/except version is recommended - don't see it as a "last resort".

This excerpt is from the official docs linked above, endorsing using try/except for flow control:

This common Python coding style assumes the existence of valid keys or attributes and catches exceptions if the assumption proves false. This clean and fast style is characterized by the presence of many try and except statements.

The instance of entity type cannot be tracked because another instance of this type with the same key is already being tracked

Without overriding EF track system, you can also Detach the 'local' entry and attach your updated entry before saving :

var local = _context.Set<YourEntity>()
    .FirstOrDefault(entry => entry.Id.Equals(entryId));

// check if local is not null 
if (local != null)
    // detach
    _context.Entry(local).State = EntityState.Detached;
// set Modified flag in your entry
_context.Entry(entryToUpdate).State = EntityState.Modified;

// save 

UPDATE: To avoid code redundancy, you can do an extension method :

public static void DetachLocal<T>(this DbContext context, T t, string entryId) 
    where T : class, IIdentifier 
    var local = context.Set<T>()
        .FirstOrDefault(entry => entry.Id.Equals(entryId));
    if (!local.IsNull())
        context.Entry(local).State = EntityState.Detached;
    context.Entry(t).State = EntityState.Modified;

My IIdentifier interface has just an Id string property.

Whatever your Entity, you can use this method on your context :

_context.DetachLocal(tmodel, id);

Automatic HTTPS connection/redirect with node.js/express

As of 0.4.12 we have no real clean way of listening for HTTP & HTTPS on the same port using Node's HTTP/HTTPS servers.

Some people have solved this issue by having having Node's HTTPS server (this works with Express.js as well) listen to 443 (or some other port) and also have a small http server bind to 80 and redirect users to the secure port.

If you absolutely have to be able to handle both protocols on a single port then you need to put nginx, lighttpd, apache, or some other web server on that port and have act as a reverse proxy for Node.

How can I issue a single command from the command line through sql plus?

This is how I solved the problem:

<target name="executeSQLScript">
    <exec executable="sqlplus" failonerror="true" errorproperty="exit.status">
        <arg value="${dbUser}/${dbPass}@<DBHOST>:<DBPORT>/<SID>"/>
        <arg value="@${basedir}/db/scripttoexecute.sql"/>

round up to 2 decimal places in java?

Try :

class round{
public static void main(String args[]){

double a = 123.13698;
double roundOff = Math.round(a*100)/100;
String.format("%.3f", roundOff); //%.3f defines decimal precision you want
System.out.println(roundOff);   }}

How to define optional methods in Swift protocol?

One option is to store them as optional function variables:

struct MyAwesomeStruct {
    var myWonderfulFunction : Optional<(Int) -> Int> = nil

let squareCalculator =
    MyAwesomeStruct(myWonderfulFunction: { input in return input * input })
let thisShouldBeFour = squareCalculator.myWonderfulFunction!(2)

I ran into a merge conflict. How can I abort the merge?

git merge --abort

Abort the current conflict resolution process, and try to reconstruct the pre-merge state.

If there were uncommitted worktree changes present when the merge started, git merge --abort will in some cases be unable to reconstruct these changes. It is therefore recommended to always commit or stash your changes before running git merge.

git merge --abort is equivalent to git reset --merge when MERGE_HEAD is present.

Pip error: Microsoft Visual C++ 14.0 is required

Try doing this:

py -m pip install pipwin
py -m pipwin install PyAudio

Mongoose.js: Find user by username LIKE value

.get(function(req, res) {

    var regex = new RegExp(, "i")
    ,   query = { description: regex };

    Product.find(query, function(err, products) {
        if (err) {



How to work with string fields in a C struct?

While Richard's is what you want if you do want to go with a typedef, I'd suggest that it's probably not a particularly good idea in this instance, as you lose sight of it being a pointer, while not gaining anything.

If you were treating it a a counted string, or something with additional functionality, that might be different, but I'd really recommend that in this instance, you just get familiar with the 'standard' C string implementation being a 'char *'...

Sort arrays of primitive types in descending order

There's been some confusion about Arrays.asList in the other answers. If you say

double[] arr = new double[]{6.0, 5.0, 11.0, 7.0};
List xs = Arrays.asList(arr);
System.out.println(xs.size());  // prints 1

then you'll have a List with 1 element. The resulting List has the double[] array as its own element. What you want is to have a List<Double> whose elements are the elements of the double[].

Unfortunately, no solution involving Comparators will work for a primitive array. Arrays.sort only accepts a Comparator when being passed an Object[]. And for the reasons describe above, Arrays.asList won't let you make a List out of the elements of your array.

So despite my earlier answer which the comments below reference, there's no better way than manually reversing the array after sorting. Any other approach (such as copying the elements into a Double[] and reverse-sorting and copying them back) would be more code and slower.

How to use std::sort to sort an array in C++

sorting method without std::sort:

// sorting myArray ascending
int iTemp = 0;
for (int i = 0; i < ARRAYSIZE; i++)
    for (int j = i + 1; j <= ARRAYSIZE; j++)
        // for descending sort change '<' with '>'
        if (myArray[j] < myArray[i])
            iTemp = myArray[i];
            myArray[i] = myArray[j];
            myArray[j] = iTemp;

Run complete example:

#include <iostream> // std::cout, std::endl /* */
#include <cstdlib>  // srand(), rand()      /* */
#include <ctime>    // time()               /* */

int main()
    const int ARRAYSIZE = 10;
    int myArray[ARRAYSIZE];

    // populate myArray with random numbers from 1 to 1000
    for (int i = 0; i < ARRAYSIZE; i++)
        myArray[i] = rand()% 1000 + 1;

    // print unsorted myArray
    std::cout << "unsorted myArray: " << std::endl;
    for (int i = 0; i < ARRAYSIZE; i++)
        std::cout << "[" << i << "] -> " << myArray[i] << std::endl;
    std::cout << std::endl;

    // sorting myArray ascending
    int iTemp = 0;
    for (int i = 0; i < ARRAYSIZE; i++)
        for (int j = i + 1; j <= ARRAYSIZE; j++)
            // for descending sort change '<' with '>'
            if (myArray[j] < myArray[i])
                iTemp = myArray[i];
                myArray[i] = myArray[j];
                myArray[j] = iTemp;

    // print sorted myArray
    std::cout << "sorted myArray: " << std::endl;
    for (int i = 0; i < ARRAYSIZE; i++)
        std::cout << "[" << i << "] -> " << myArray[i] << std::endl;
    std::cout << std::endl;

    return 0;

How to Upload Image file in Retrofit 2

Upload Image See Here click This Linkenter image description here

import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

class AppConfig {

    private static String BASE_URL = "";

    static Retrofit getRetrofit() {

        return new Retrofit.Builder()

import okhttp3.MultipartBody;
import okhttp3.RequestBody;
import retrofit2.Call;
import retrofit2.http.Multipart;
import retrofit2.http.POST;
import retrofit2.http.Part;

interface ApiConfig {
    Call<ServerResponse> uploadFile(@Part MultipartBody.Part file,
                                    @Part("file") RequestBody name);

    Call<ServerResponseKeshav> uploadFile(@Part MultipartBody.Part file,
                                    @Part("file") RequestBody name);*/

    Call<ServerResponse> uploadMulFile(@Part MultipartBody.Part file1,
                                       @Part MultipartBody.Part file2);


Create an empty object in JavaScript with {} or new Object()?

This is essentially the same thing. Use whatever you find more convenient.

HTML input file selection event not firing upon selecting the same file

Do whatever you want to do after the file loads successfully.just after the completion of your file processing set the value of file control to blank the .change() will always be called even the file name changes or not. like for example you can do this thing and worked for me like charm

   $('#myFile').change(function () {
       LoadFile("myFile");//function to do processing of file.
       $('#myFile').val('');// set the value to empty of myfile control.

What is the difference between ng-if and ng-show/ng-hide

Maybe an interesting point to make, is the difference between priorities between both.

As far as I can tell, the ng-if directive has one of the highest (if not the highest) priority of all Angular directives. Which means: it will run FIRST before all other, lower prioritised, directives. The fact that it runs FIRST, means that effectively, the element is removed before any inner directives are processed. Or at least: that's what I make of it.

I observerd and used this in the UI I'm building for my current customer. The entire UI is quite heavily packed, and it had ng-show and ng-hide all over it. Not to go into too much detail, but I built a generic component, which could be managed using JSON config, so I had to do some switching inside the template. There is an ng-repeat present, and inside the ng-repeat, a table is shown, which has a lot of ng-shows, ng-hides and even ng-switches present. They wanted to show at least 50 repeats in the list, which would result in more or less 1500-2000 directives to be resolved. I checked the code, and the Java backend + custom JS on the front would take about 150ms to process the data, and then Angular would chew some 2-3 seconds on it, before displaying. The customer did not complain, but I was appalled :-)

In my search, I stumbled across the ng-if directive. Now, maybe it's best to point out that at the point of conceiving this UI, there was no ng-if available. Because the ng-show and ng-hide had functions in them, which returned booleans, I could easily replace them all with ng-if. By doing so, all inner directives seemed to be no longer evaluated. That meant that I dropped back to about a third of all directives being evaluated, and thus, the UI speeded up to about 500ms - 1 sec loading time. (I have no way to determine exact seconds)

Do note: the fact that the directives are not evaluated, is an educated guess about what is happening underneath.

So, in my opinion: if you need the element to be present on the page (ie: for checking the element, or whatever), but simply be hidden, use ng-show/ng-hide. In all other cases, use ng-if.

Bootstrap dropdown menu not working (not dropping down when clicked)

Just Remove the type="text/javascript"

<script src="JavaScript/jquery.js" />
<script src="JavaScript/bootstrap-min.js" />

Here is the update -

How do I make a self extract and running installer

Okay I have got it working, hope this information is useful.

  1. First of all I now realize that not only do self-extracting zip start extracting with doubleclick, but they require no extraction application to be installed on the users computer because the extractor code is in the archive itself. This means that you will get a different user experience depending on what you application you use to create the sfx

  2. I went with WinRar as follows, this does not require you to create an sfx file, everything can be created via the gui:

    • Select files, right click and select Add to Archive
    • Use Browse.. to create the archive in the folder above
    • Change Archive Format to Zip
    • Enable Create SFX archive
    • Select Advanced tab
    • Select SFX Options
    • Select Setup tab
    • Enter setup.exe into the Run after Extraction field
    • Select Modes tab
    • Enable Unpack to temporary folder
    • Select text and Icon tab
    • Enter a more appropriate title for your task
    • Select OK
    • Select OK

The resultant exe unzips to a temporary folder and then starts the installer

Uncaught ReferenceError: angular is not defined - AngularJS not working

As you know angular.module( declared under angular.js file.So before accessing angular.module, you must have make it available by using <script src="lib/angular/angular.js"></script>(In your case) after then you can call angular.module. It will work.


<html lang="en">
  <meta charset="utf-8">
  <title>My AngularJS App</title>
  <link rel="stylesheet" href="css/app.css"/>
<!-- In production use:
  <script src="//"></script>
  <script src="lib/angular/angular.js"></script>
  <script src="lib/angular/angular-route.js"></script>
  <script src="js/app.js"></script>
  <script src="js/services.js"></script>
  <script src="js/controllers.js"></script>
  <script src="js/filters.js"></script>
  <script src="js/directives.js"></script>

        var app = angular.module('myApp',[]);


            return function(scope, element,attrs) {
                element.bind('click',function() {alert('click')});

<body ng-app="myApp">
    <div >
        <button my-directive>Click Me!</button>


Error: Cannot find module 'ejs'

I ran into this problem after I forgot to install ejs before the first time I ran my app. For some reason ejs was not being seen after installing it later. I found a quick, clean, and effective solution to this problem which was to reinstall express by running npm uninstall express then npm install express in the local directory before restarting the server.

How to present a simple alert message in java?

I'll be the first to admit Java can be very verbose, but I don't think this is unreasonable:

JOptionPane.showMessageDialog(null, "My Goodness, this is so concise");

If you statically import javax.swing.JOptionPane.showMessageDialog using:

import static javax.swing.JOptionPane.showMessageDialog;

This further reduces to

showMessageDialog(null, "This is even shorter");

Better way to set distance between flexbox items

I have used this for wrapped and fixed width columns. The key here is calc()

SCSS sample

$gap: 10px;

dl {
  display: flex;
  flex-wrap: wrap;
  padding: $gap/2;

  dt, dd {
    margin: $gap/2;}

  dt { // full width, acts as header
    flex: 0 0 calc(100% - #{$gap});}

  dd { // default grid: four columns 
    flex: 0 0 calc(25% - #{$gap});}

  .half { // hall width columns
    flex: 0 0 calc(50% - #{$gap});}


Full Codepen sample

How to solve maven 2.6 resource plugin dependency?

This issue is happening due to change of protocol from http to https for central repository. please refer following link for more details. 

In order to fix the problem, copy following into your file. This will set the repository url to use https.

            <name>Central Repository</name>
            <name>Central Repository</name>

Python Pandas merge only certain columns

If you want to drop column(s) from the target data frame, but the column(s) are required for the join, you can do the following:

df1 = df1.merge(df2[['a', 'b', 'key1']], how = 'left',
                left_on = 'key2', right_on = 'key1').drop('key1')

The .drop('key1') part will prevent 'key1' from being kept in the resulting data frame, despite it being required to join in the first place.

How to export library to Jar in Android Studio?

I was able to export a jar file in Android Studio using this tutorial: "How To Export Jar From Android Studio "

I updated my answer to include all the steps for exporting a JAR in Android Studio:

1) Create Android application project, go to app->build.gradle

2) Change the following in this file:

  • modify apply plugin: '' to apply plugin: ''

  • remove the following: applicationId, versionCode and versionName

  • Add the following code:

// Task to delete old jar
task deleteOldJar(type: Delete){
   delete 'release/AndroidPlugin2.jar'
// task to export contents as jar
task exportJar(type: Copy) {
    from ('build/intermediates/bundles/release/')
    into ('release/')
    include ('classes.jar')
    rename('classes.jar', 'AndroidPlugin2.jar')
exportJar.dependsOn(deleteOldJar, build)

3) Don't forget to click sync now in this file (top right or use sync button).

4) Click on Gradle tab (usually middle right) and scroll down to exportjar

5) Once you see the build successful message in the run window, using normal file explorer go to exported jar using the path: C:\Users\name\AndroidStudioProjects\ProjectName\app\release you should see in this directory your jar file.

Good Luck :)

How do I get a value of a <span> using jQuery?

    $(document).ready(function () {

            $.each($(".classBalence").find("span"), function () {
            if ($(this).text() >1) {
                $(this).css("color", "green")

            if ($(this).text() < 1) {
                $(this).css("color", "red")
                $(this).css("font-weight", "bold")


How to create SPF record for multiple IPs?

Yes the second syntax is fine.

Have you tried using the SPF wizard?

It can quickly generate basic and complex SPF records.

Multiple conditions in WHILE loop

If your code, if the user enters 'X' (for instance), when you reach the while condition evaluation it will determine that 'X' is differente from 'n' (nChar != 'n') which will make your loop condition true and execute the code inside of your loop. The second condition is not even evaluated.

Can Android Studio be used to run standard Java projects?

I have been able to do it using following steps:

  1. Open Android Studio and select 'Import Project'.
    Android Studio import a project

  2. Browse to your project folder in the browse window and select it.

C# difference between == and Equals()

There is another dimension to an earlier answer by @BlueMonkMN. The additional dimension is that the answer to the @Drahcir's title question as it is stated also depends on how we arrived at the string value. To illustrate:

string s1 = "test";
string s2 = "test";
string s3 = "test1".Substring(0, 4);
object s4 = s3;
string s5 = "te" + "st";
object s6 = s5;
Console.WriteLine("{0} {1} {2}", object.ReferenceEquals(s1, s2), s1 == s2, s1.Equals(s2));

Console.WriteLine("\n  Case1 - A method changes the value:");
Console.WriteLine("{0} {1} {2}", object.ReferenceEquals(s1, s3), s1 == s3, s1.Equals(s3));
Console.WriteLine("{0} {1} {2}", object.ReferenceEquals(s1, s4), s1 == s4, s1.Equals(s4));

Console.WriteLine("\n  Case2 - Having only literals allows to arrive at a literal:");
Console.WriteLine("{0} {1} {2}", object.ReferenceEquals(s1, s5), s1 == s5, s1.Equals(s5));
Console.WriteLine("{0} {1} {2}", object.ReferenceEquals(s1, s6), s1 == s6, s1.Equals(s6));

The output is:

True True True

  Case1 - A method changes the value:
False True True
False False True

  Case2 - Having only literals allows to arrive at a literal:
True True True
True True True

Convert string to int array using LINQ

You can shorten JSprangs solution a bit by using a method group instead:

string s1 = "1;2;3;4;5;6;7;8;9;10;11;12";
int[] ints = s1.Split(';').Select(int.Parse).ToArray();

How can I read SMS messages from the device programmatically in Android?

The easiest function

To read the sms I wrote a function that returns a Conversation object:

class Conversation(val number: String, val message: List<Message>)
class Message(val number: String, val body: String, val date: Date)

fun getSmsConversation(context: Context, number: String? = null, completion: (conversations: List<Conversation>?) -> Unit) {
        val cursor = context.contentResolver.query(Telephony.Sms.CONTENT_URI, null, null, null, null)

        val numbers = ArrayList<String>()
        val messages = ArrayList<Message>()
        var results = ArrayList<Conversation>()

        while (cursor != null && cursor.moveToNext()) {
            val smsDate = cursor.getString(cursor.getColumnIndexOrThrow(Telephony.Sms.DATE))
            val number = cursor.getString(cursor.getColumnIndexOrThrow(Telephony.Sms.ADDRESS))
            val body = cursor.getString(cursor.getColumnIndexOrThrow(Telephony.Sms.BODY))

            messages.add(Message(number, body, Date(smsDate.toLong())))


        numbers.forEach { number ->
            if (results.find { it.number == number } == null) {
                val msg = messages.filter { it.number == number }
                results.add(Conversation(number = number, message = msg))

        if (number != null) {
            results = results.filter { it.number == number } as ArrayList<Conversation>



getSmsConversation(this){ conversations ->
    conversations.forEach { conversation ->
        println("Number: ${conversation.number}")
        println("Message One: ${conversation.message[0].body}")
        println("Message Two: ${conversation.message[1].body}")

Or get only conversation of specific number:

getSmsConversation(this, "+33666494128"){ conversations ->
    conversations.forEach { conversation ->
        println("Number: ${conversation.number}")
        println("Message One: ${conversation.message[0].body}")
        println("Message Two: ${conversation.message[1].body}")

SHA-256 or MD5 for file integrity

To 1): Yes, on most CPUs, SHA-256 is about only 40% as fast as MD5.

To 2): I would argue for a different algorithm than MD5 in such a case. I would definitely prefer an algorithm that is considered safe. However, this is more a feeling. Cases where this matters would be rather constructed than realistic, e.g. if your backup system encounters an example case of an attack on an MD5-based certificate, you are likely to have two files in such an example with different data, but identical MD5 checksums. For the rest of the cases, it doesn't matter, because MD5 checksums have a collision (= same checksums for different data) virtually only when provoked intentionally. I'm not an expert on the various hashing (checksum generating) algorithms, so I can not suggest another algorithm. Hence this part of the question is still open. Suggested further reading is Cryptographic Hash Function - File or Data Identifier on Wikipedia. Also further down on that page there is a list of cryptographic hash algorithms.

To 3): MD5 is an algorithm to calculate checksums. A checksum calculated using this algorithm is then called an MD5 checksum.

EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) on dispatch_semaphore_dispose

In my case:

PHImageRequestOptions *requestOptions = [PHImageRequestOptions new];
requestOptions.synchronous            = NO;

Was trying to do this with dispatch_group

Django: Model Form "object has no attribute 'cleaned_data'"

For some reason, you're re-instantiating the form after you check is_valid(). Forms only get a cleaned_data attribute when is_valid() has been called, and you haven't called it on this new, second instance.

Just get rid of the second form = SearchForm(request.POST) and all should be well.

How do I declare a model class in my Angular 2 component using TypeScript?

The problem lies that you haven't added Model to either the bootstrap (which will make it a singleton), or to the providers array of your component definition:

    selector: "testWidget",
    template: "<div>This is a test and {{param1}} is my param.</div>",
    providers : [

export class testWidget {
    constructor(private model: Model) {}

And yes, you should define Model above the Component. But better would be to put it in his own file.

But if you want it to be just a class from which you can create multiple instances, you better just use new.

    selector: "testWidget",
    template: "<div>This is a test and {{param1}} is my param.</div>"

export class testWidget {

    private model: Model = new Model();

    constructor() {}

Calculating difference between two timestamps in Oracle in milliseconds

Select date1 - (date2 - 1) * 24 * 60 *60 * 1000 from Table;

How to call shell commands from Ruby

The backticks (`) method is the easiest one to call shell commands from Ruby. It returns the result of the shell command:

     url_request = ''
     result_of_shell_command = `curl #{url_request}`

Create a SQL query to retrieve most recent records

The derived table would work, but if this is SQL 2005, a CTE and ROW_NUMBER might be cleaner:

WITH UserStatus (User, Date, Status, Notes, Ord)
SELECT Date, User, Status, Notes, 

SELECT User, Date, Status, Notes from UserStatus where Ord = 1

This would also facilitate the display of the most recent x statuses from each user.

What is difference between monolithic and micro kernel?

Monolithic kernel has all kernel services along with kernel core part, thus are heavy and has negative impact on speed and performance. On the other hand micro kernel is lightweight causing increase in performance and speed.
I answered same question at wordpress site. For the difference between monolithic, microkernel and exokernel in tabular form, you can visit here

What are Covering Indexes and Covered Queries in SQL Server?

Page 178, High Performance MySQL, 3rd Edition

An index that contains (or "covers") all the data needed to satisfy a query is called a covering index.

When you issue a query that is covered by an index (an indexed-covered query), you'll see "Using Index" in the Extra column in EXPLAIN.

How to add browse file button to Windows Form using C#

These links explain it with examples

private void button1_Click(object sender, EventArgs e)
    int size = -1;
    DialogResult result = openFileDialog1.ShowDialog(); // Show the dialog.
    if (result == DialogResult.OK) // Test result.
       string file = openFileDialog1.FileName;
          string text = File.ReadAllText(file);
          size = text.Length;
       catch (IOException)
    Console.WriteLine(size); // <-- Shows file size in debugging mode.
    Console.WriteLine(result); // <-- For debugging use.

Creating random numbers with no duplicates

You could use one of the classes implementing the Set interface (API), and then each number you generate, use Set.add() to insert it.

If the return value is false, you know the number has already been generated before.

Generate a unique id

Why not just use ToString?

public string generateID()
    return Guid.NewGuid().ToString("N");

If you would like it to be based on a URL, you could simply do the following:

public string generateID(string sourceUrl)
    return string.Format("{0}_{1:N}", sourceUrl, Guid.NewGuid());

If you want to hide the URL, you could use some form of SHA1 on the sourceURL, but I'm not sure what that might achieve.

Is there a NumPy function to return the first index of something in an array?

If you need the index of the first occurrence of only one value, you can use nonzero (or where, which amounts to the same thing in this case):

>>> t = array([1, 1, 1, 2, 2, 3, 8, 3, 8, 8])
>>> nonzero(t == 8)
(array([6, 8, 9]),)
>>> nonzero(t == 8)[0][0]

If you need the first index of each of many values, you could obviously do the same as above repeatedly, but there is a trick that may be faster. The following finds the indices of the first element of each subsequence:

>>> nonzero(r_[1, diff(t)[:-1]])
(array([0, 3, 5, 6, 7, 8]),)

Notice that it finds the beginning of both subsequence of 3s and both subsequences of 8s:

[1, 1, 1, 2, 2, 3, 8, 3, 8, 8]

So it's slightly different than finding the first occurrence of each value. In your program, you may be able to work with a sorted version of t to get what you want:

>>> st = sorted(t)
>>> nonzero(r_[1, diff(st)[:-1]])
(array([0, 3, 5, 7]),)

Select rows of a matrix that meet a condition

If your matrix is called m, just use :

R> m[m$three == 11, ]

When is it appropriate to use C# partial classes?

Partial classes make it possible to add functionality to a suitably-designed program merely by adding source files. For example, a file-import program could be designed so that one could add different types of known files by adding modules that handle them. For example, the main file type converter could include a small class:

Partial Public Class zzFileConverterRegistrar
    Event Register(ByVal mainConverter as zzFileConverter)
    Sub registerAll(ByVal mainConverter as zzFileConverter)
        RaiseEvent Register(mainConverter)
    End Sub
End Class

Each module that wishes to register one or more types of file converter could include something like:

Partial Public Class zzFileConverterRegistrar
    Private Sub RegisterGif(ByVal mainConverter as zzFileConverter) Handles Me.Register
        mainConverter.RegisterConverter("GIF", GifConverter.NewFactory))
    End Sub
End Class

Note that the main file converter class isn't "exposed"--it just exposes a little stub class that add-in modules can hook to. There is a slight risk of naming conflicts, but if each add-in module's "register" routine is named according to the type of file it deals with, they probably shouldn't pose a problem. One could stick a GUID in the name of the registration subroutine if one were worried about such things.

Edit/Addendum To be clear, the purpose of this is to provide a means by which a variety of separate classes can let a main program or class know about them. The only thing the main file converter will do with zzFileConverterRegistrar is create one instance of it and call the registerAll method which will fire the Register event. Any module that wants to hook that event can execute arbitrary code in response to it (that's the whole idea) but there isn't anything a module could do by improperly extending the zzFileConverterRegistrar class other than define a method whose name matches that of something else. It would certainly be possible for one improperly-written extension to break another improperly-written extension, but the solution for that is for anyone who doesn't want his extension broken to simply write it properly.

One could, without using partial classes, have a bit of code somewhere within the main file converter class, which looked like:

  RegisterConverter("GIF", GifConvertor.NewFactory)
  RegisterConverter("BMP", BmpConvertor.NewFactory)
  RegisterConverter("JPEG", JpegConvertor.NewFactory)

but adding another converter module would require going into that part of the converter code and adding the new converter to the list. Using partial methods, that is no longer necessary--all converters will get included automatically.

Getting "Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?" when installing lxml through pip

In case anyone else has the same issue as this on

Centos, try:

yum install python-lxml


sudo apt-get install -y python-lxml

worked for me.

How to add parameters into a WebRequest?

I have a feeling that the username and password that you are sending should be part of the Authorization Header. So the code below shows you how to create the Base64 string of the username and password. I also included an example of sending the POST data. In my case it was a phone_number parameter.

string credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes(_username + ":" + _password));

HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(Request);
webRequest.Headers.Add("Authorization", string.Format("Basic {0}", credentials));
webRequest.ContentType = "application/x-www-form-urlencoded";
webRequest.Method = WebRequestMethods.Http.Post;
webRequest.AllowAutoRedirect = true;
webRequest.Proxy = null;

string data = "phone_number=19735559042"; 
byte[] dataStream = Encoding.UTF8.GetBytes(data);

request.ContentLength = dataStream.Length;
Stream newStream = webRequest.GetRequestStream();
newStream.Write(dataStream, 0, dataStream.Length);

HttpWebResponse response = (HttpWebResponse)webRequest.GetResponse();
Stream stream = response.GetResponseStream();
StreamReader streamreader = new StreamReader(stream);
string s = streamreader.ReadToEnd();

How do you create a Distinct query in HQL

Suppose you have a Customer Entity mapped to CUSTOMER_INFORMATION table and you want to get list of distinct firstName of customer. You can use below snippet to get the same.

Query distinctFirstName = session.createQuery("select ci.firstName from Customer ci group by ci.firstName");
Object [] firstNamesRows = distinctFirstName.list();

I hope it helps. So here we are using group by instead of using distinct keyword.

Also previously I found it difficult to use distinct keyword when I want to apply it to multiple columns. For example I want of get list of distinct firstName, lastName then group by would simply work. I had difficulty in using distinct in this case.

Regex allow digits and a single dot

Try this

boxValue = boxValue.replace(/[^0-9\.]/g,"");

This Regular Expression will allow only digits and dots in the value of text box.

Oracle: Import CSV file

From Oracle 18c you could use Inline External Tables:

Inline external tables enable the runtime definition of an external table as part of a SQL statement, without creating the external table as persistent object in the data dictionary.

With inline external tables, the same syntax that is used to create an external table with a CREATE TABLE statement can be used in a SELECT statement at runtime. Specify inline external tables in the FROM clause of a query block. Queries that include inline external tables can also include regular tables for joins, aggregation, and so on.

INSERT INTO target_table(time_id, prod_id, quantity_sold, amount_sold)
SELECT time_id, prod_id, quantity_sold, amount_sold
    (time_id        DATE NOT NULL,     
     prod_id        INTEGER NOT NULL,
     quantity_sold  NUMBER(10,2),
     amount_sold    NUMBER(10,2))     
      FIELDS TERMINATED BY '|')     
   LOCATION ('sales_9.csv') REJECT LIMIT UNLIMITED) sales_external;

How to read keyboard-input?

It seems that you are mixing different Pythons here (Python 2.x vs. Python 3.x)... This is basically correct:

nb = input('Choose a number: ')

The problem is that it is only supported in Python 3. As @sharpner answered, for older versions of Python (2.x), you have to use the function raw_input:

nb = raw_input('Choose a number: ')

If you want to convert that to a number, then you should try:

number = int(nb)

... though you need to take into account that this can raise an exception:

    number = int(nb)
except ValueError:
    print("Invalid number")

And if you want to print the number using formatting, in Python 3 str.format() is recommended:

print("Number: {0}\n".format(number))

Instead of:

print('Number %s \n' % (nb))

But both options (str.format() and %) do work in both Python 2.7 and Python 3.

Mobile website "WhatsApp" button to send message to a specific number

On android, you can try


replace [countrycode_without_plus][number] with the number,

Best practice for Django project working directory structure

There're two kind of Django "projects" that I have in my ~/projects/ directory, both have a bit different structure.:

  • Stand-alone websites
  • Pluggable applications

Stand-alone website

Mostly private projects, but doesn't have to be. It usually looks like this:


docs/               # documentation
scripts/         # installed to PATH via
project_name/       # project dir (the one which creates)
  apps/             # project-specific applications
    accounts/       # most frequent app, with custom user model
  settings/         # settings for different environments, see below
        # contains project version
static/             # site-specific static files
templates/          # site-specific templates
tests/              # site-specific tests (mostly in-browser ones)
tmp/                # excluded from git


The main settings are production ones. Other files (eg., simply import everything from and override only necessary variables.

For each environment, there are separate settings files, eg. production, development. I some projects I have also testing (for test runner), staging (as a check before final deploy) and heroku (for deploying to heroku) settings.


I rather specify requirements in directly. Only those required for development/test environment I have in requirements_dev.txt.

Some services (eg. heroku) requires to have requirements.txt in root directory.

Useful when deploying project using setuptools. It adds to PATH, so I can run directly (anywhere).

Project-specific apps

I used to put these apps into project_name/apps/ directory and import them using relative imports.

Templates/static/locale/tests files

I put these templates and static files into global templates/static directory, not inside each app. These files are usually edited by people, who doesn't care about project code structure or python at all. If you are full-stack developer working alone or in a small team, you can create per-app templates/static directory. It's really just a matter of taste.

The same applies for locale, although sometimes it's convenient to create separate locale directory.

Tests are usually better to place inside each app, but usually there is many integration/functional tests which tests more apps working together, so global tests directory does make sense.

Tmp directory

There is temporary directory in project root, excluded from VCS. It's used to store media/static files and sqlite database during development. Everything in tmp could be deleted anytime without any problems.


I prefer virtualenvwrapper and place all venvs into ~/.venvs directory, but you could place it inside tmp/ to keep it together.

Project template

I've created project template for this setup, django-start-template


Deployment of this project is following:

source $VENV/bin/activate
export DJANGO_SETTINGS_MODULE=project_name.settings.production
git pull
pip install -r requirements.txt

# Update database, static files, locales syncdb  --noinput migrate collectstatic --noinput makemessages -a compilemessages

# restart wsgi
touch project_name/

You can use rsync instead of git, but still you need to run batch of commands to update your environment.

Recently, I made django-deploy app, which allows me to run single management command to update environment, but I've used it for one project only and I'm still experimenting with it.

Sketches and drafts

Draft of templates I place inside global templates/ directory. I guess one can create folder sketches/ in project root, but haven't used it yet.

Pluggable application

These apps are usually prepared to publish as open-source. I've taken example below from django-forme



Name of directories is clear (I hope). I put test files outside app directory, but it really doesn't matter. It is important to provide README and, so package is easily installed through pip.

Use formula in custom calculated field in Pivot Table

I'll post this comment as answer, as I'm confident enough that what I asked is not possible.

I) Couple of similar questions trying to do the same, without success:

II) This article: Excel Pivot Table Calculated Field for example lists many restrictions of Calculated Field:

  • For calculated fields, the individual amounts in the other fields are summed, and then the calculation is performed on the total amount.
  • Calculated field formulas cannot refer to the pivot table totals or subtotals
  • Calculated field formulas cannot refer to worksheet cells by address or by name.
  • Sum is the only function available for a calculated field.
  • Calculated fields are not available in an OLAP-based pivot table.

III) There is tiny limited possibility to use AVERAGE() and similar function for a range of cells, but that applies only if Pivot table doesn't have grouped cells, which allows listing the cells as items in new group (right to "Fileds" listbox in above screenshot) and then user can calculate AVERAGE(), referencing explicitly every item (cell), from Items listbox, as argument. Maybe it's better explained here: Calculate values in a PivotTable report
For my Pivot table it wasn't applicable because my range wasn't small enough, this option to be sane choice.

Abstract methods in Java

The error message tells the exact reason: "abstract methods cannot have a body".

They can only be defined in abstract classes and interfaces (interface methods are implicitly abstract!) and the idea is, that the subclass implements the method.


 public abstract class AbstractGreeter {
   public abstract String getHelloMessage();

   public void sayHello() {

 public class FrenchGreeter extends AbstractGreeter{

   // we must implement the abstract method
   public String getHelloMessage() {
     return "bonjour";

How to enable/disable bluetooth programmatically in android

Android BluetoothAdapter docs say it has been available since API Level 5. API Level 5 is Android 2.0.

You can try using a backport of the Bluetooth API (have not tried it personally):

Subdomain on different host

sub domain is part of the domain, it's like subletting a room of an apartment. A records has to be setup on the dns for the domain e.g has IP 123.456.789.999 and hosted with Godaddy. Now to get the sub domain

of which the site is actually on another server then

login to Godaddy and add an A record dnsimple and point the IP to the other server

And that's it.

Sorting an IList in C#

The accepted answer by @DavidMills is quite good, but I think it can be improved upon. For one, there is no need to define the ComparisonComparer<T> class when the framework already includes a static method Comparer<T>.Create(Comparison<T>). This method can be used to create an IComparison on the fly.

Also, it casts IList<T> to IList which has the potential to be dangerous. In most cases that I have seen, List<T> which implements IList is used behind the scenes to implement IList<T>, but this is not guaranteed and can lead to brittle code.

Lastly, the overloaded List<T>.Sort() method has 4 signatures and only 2 of them are implemented.

  1. List<T>.Sort()
  2. List<T>.Sort(Comparison<T>)
  3. List<T>.Sort(IComparer<T>)
  4. List<T>.Sort(Int32, Int32, IComparer<T>)

The below class implements all 4 List<T>.Sort() signatures for the IList<T> interface:

using System;
using System.Collections.Generic;

public static class IListExtensions
    public static void Sort<T>(this IList<T> list)
        if (list is List<T>)
            List<T> copy = new List<T>(list);
            Copy(copy, 0, list, 0, list.Count);

    public static void Sort<T>(this IList<T> list, Comparison<T> comparison)
        if (list is List<T>)
            List<T> copy = new List<T>(list);
            Copy(copy, 0, list, 0, list.Count);

    public static void Sort<T>(this IList<T> list, IComparer<T> comparer)
        if (list is List<T>)
            List<T> copy = new List<T>(list);
            Copy(copy, 0, list, 0, list.Count);

    public static void Sort<T>(this IList<T> list, int index, int count,
        IComparer<T> comparer)
        if (list is List<T>)
            ((List<T>)list).Sort(index, count, comparer);
            List<T> range = new List<T>(count);
            for (int i = 0; i < count; i++)
                range.Add(list[index + i]);
            Copy(range, 0, list, index, count);

    private static void Copy<T>(IList<T> sourceList, int sourceIndex,
        IList<T> destinationList, int destinationIndex, int count)
        for (int i = 0; i < count; i++)
            destinationList[destinationIndex + i] = sourceList[sourceIndex + i];


class Foo
    public int Bar;

    public Foo(int bar) { this.Bar = bar; }

void TestSort()
    IList<int> ints = new List<int>() { 1, 4, 5, 3, 2 };
    IList<Foo> foos = new List<Foo>()
        new Foo(1),
        new Foo(4),
        new Foo(5),
        new Foo(3),
        new Foo(2),

    foos.Sort((x, y) => Comparer<int>.Default.Compare(x.Bar, y.Bar));

The idea here is to leverage the functionality of the underlying List<T> to handle sorting whenever possible. Again, most IList<T> implementations that I have seen use this. In the case when the underlying collection is a different type, fallback to creating a new instance of List<T> with elements from the input list, use it to do the sorting, then copy the results back to the input list. This will work even if the input list does not implement the IList interface.

What is the usefulness of PUT and DELETE HTTP request methods?

Safe Methods : Get Resource/No modification in resource
Idempotent : No change in resource status if requested many times
Unsafe Methods : Create or Update Resource/Modification in resource
Non-Idempotent : Change in resource status if requested many times

According to your requirement :

1) For safe and idempotent operation (Fetch Resource) use --------- GET METHOD
2) For unsafe and non-idempotent operation (Insert Resource) use--------- POST METHOD
3) For unsafe and idempotent operation (Update Resource) use--------- PUT METHOD
3) For unsafe and idempotent operation (Delete Resource) use--------- DELETE METHOD

How can I use Guzzle to send a POST request in JSON?

$client = new \GuzzleHttp\Client();

$body['grant_type'] = "client_credentials";
$body['client_id'] = $this->client_id;
$body['client_secret'] = $this->client_secret;

$res = $client->post($url, [ 'body' => json_encode($body) ]);

$code = $res->getStatusCode();
$result = $res->json();

Returning binary file from controller in ASP.NET Web API

While the suggested solution works fine, there is another way to return a byte array from the controller, with response stream properly formatted :

  • In the request, set header "Accept: application/octet-stream".
  • Server-side, add a media type formatter to support this mime type.

Unfortunately, WebApi does not include any formatter for "application/octet-stream". There is an implementation here on GitHub: BinaryMediaTypeFormatter (there are minor adaptations to make it work for webapi 2, method signatures changed).

You can add this formatter into your global config :

HttpConfiguration config;
// ...
config.Formatters.Add(new BinaryMediaTypeFormatter(false));

WebApi should now use BinaryMediaTypeFormatter if the request specifies the correct Accept header.

I prefer this solution because an action controller returning byte[] is more comfortable to test. Though, the other solution allows you more control if you want to return another content-type than "application/octet-stream" (for example "image/gif").

Extract substring from a string

When finding multiple occurrences of a substring matching a pattern

    String input_string = "foo/adsfasdf/adf/bar/erqwer/";
    String regex = "(foo/|bar/)"; // Matches 'foo/' and 'bar/'

    Pattern pattern = Pattern.compile(regex);
    Matcher matcher = pattern.matcher(input_string);

    while(matcher.find()) {
      String str_matched = input_string.substring(matcher.start(), matcher.end());
        // Do something with a match found

Filtering a spark dataframe based on date

Don't use this as suggested in other answers

.filter(f.col("dateColumn") < f.lit('2017-11-01'))

But use this instead

.filter(f.col("dateColumn") < f.unix_timestamp(f.lit('2017-11-01 00:00:00')).cast('timestamp'))

This will use the TimestampType instead of the StringType, which will be more performant in some cases. For example Parquet predicate pushdown will only work with the latter.

What is the difference between Digest and Basic Authentication?

Let us see the difference between the two HTTP authentication using Wireshark (Tool to analyse packets sent or received) .

1. Http Basic Authentication


As soon as the client types in the correct username:password,as requested by the Web-server, the Web-Server checks in the Database if the credentials are correct and gives the access to the resource .

Here is how the packets are sent and received :

enter image description here In the first packet the Client fill the credentials using the POST method at the resource - lab/webapp/basicauth .In return the server replies back with http response code 200 ok ,i.e, the username:password were correct .

Detail of HTTP packet

Now , In the Authorization header it shows that it is Basic Authorization followed by some random string .This String is the encoded (Base64) version of the credentials admin:aadd (including colon ) .

2 . Http Digest Authentication(rfc 2069)

So far we have seen that the Basic Authentication sends username:password in plaintext over the network .But the Digest Auth sends a HASH of the Password using Hash algorithm.

Here are packets showing the requests made by the client and response from the server .


As soon as the client types the credentials requested by the server , the Password is converted to a response using an algorithm and then is sent to the server , If the server Database has same response as given by the client the server gives the access to the resource , otherwise a 401 error .

Detailed digest auth packet In the above Authorization , the response string is calculated using the values of Username,Realm,Password,http-method,URI and Nonce as shown in the image :

Response algorithm (colons are included)

Hence , we can see that the Digest Authentication is more Secure as it involve Hashing (MD5 encryption) , So the packet sniffer tools cannot sniff the Password although in Basic Auth the exact Password was shown on Wireshark.

How to change default JRE for all Eclipse workspaces?

when you select run configuration, there is a JRE tap up next the main tap, select "Workspace default JRE(JDK1.7)".

Be sure to use the jdk in Prefs->Java->Installed JREs ->Execution Environment

Squaring all elements in a list

Use a list comprehension (this is the way to go in pure Python):

>>> l = [1, 2, 3, 4]
>>> [i**2 for i in l]
[1, 4, 9, 16]

Or numpy (a well-established module):

>>> numpy.array([1, 2, 3, 4])**2
array([ 1,  4,  9, 16])

In numpy, math operations on arrays are, by default, executed element-wise. That's why you can **2 an entire array there.

Other possible solutions would be map-based, but in this case I'd really go for the list comprehension. It's Pythonic :) and a map-based solution that requires lambdas is slower than LC.

Nodejs send file in response

You need use Stream to send file (archive) in a response, what is more you have to use appropriate Content-type in your response header.

There is an example function that do it:

const fs = require('fs');

// Where fileName is name of the file and response is Node.js Reponse. 
responseFile = (fileName, response) => {
  const filePath =  "/path/to/archive.rar" // or any file format

  // Check if file specified by the filePath exists 
  fs.exists(filePath, function(exists){
      if (exists) {     
        // Content-type is very interesting part that guarantee that
        // Web browser will handle response in an appropriate manner.
        response.writeHead(200, {
          "Content-Type": "application/octet-stream",
          "Content-Disposition": "attachment; filename=" + fileName
      } else {
        response.writeHead(400, {"Content-Type": "text/plain"});
        response.end("ERROR File does not exist");

The purpose of the Content-Type field is to describe the data contained in the body fully enough that the receiving user agent can pick an appropriate agent or mechanism to present the data to the user, or otherwise deal with the data in an appropriate manner.

"application/octet-stream" is defined as "arbitrary binary data" in RFC 2046, purpose of this content-type is to be saved to disk - it is what you really need.

"filename=[name of file]" specifies name of file which will be downloaded.

For more information please see this stackoverflow topic.

I want to use CASE statement to update some records in sql server 2005

If you don't want to repeat the list twice (as per @J W's answer), then put the updates in a table variable and use a JOIN in the UPDATE:

declare @ToDo table (FromName varchar(10), ToName varchar(10))
insert into @ToDo(FromName,ToName) values

update ts set LastName = ToName
from dbo.TestStudents ts
       inner join
     @ToDo t
         ts.LastName = t.FromName

R command for setting working directory to source file location in Rstudio

I understand this is outdated, but I couldn't get the former answers to work very satisfactorily, so I wanted to contribute my method in case any one else encounters the same error mentioned in the comments to BumbleBee's answer.

Mine is based on a simple system command. All you feed the function is the name of your script:

extractRootDir <- function(x) {
    abs <- suppressWarnings(system(paste("find ./ -name",x), wait=T, intern=T, ignore.stderr=T))[1];
    path <- paste("~",substr(abs, 3, length(strsplit(abs,"")[[1]])),sep="");
    ret <- gsub(x, "", path);


The output from the function would look like "/Users/you/Path/To/Script". Hope this helps anyone else who may have gotten stuck.

Problems with Android Fragment back stack

I know it's a old quetion but i got the same problem and fix it like this:

First, Add Fragment1 to BackStack with a name (e.g "Frag1"):

frag = new Fragment1();

transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(, frag);

And then, Whenever you want to go back to Fragment1 (even after adding 10 fragments above it), just call popBackStackImmediate with the name:

getSupportFragmentManager().popBackStackImmediate("Frag1", 0);

Hope it will help someone :)

Run command on the Ansible host

You can use delegate_to to run commands on your Ansible host (admin host), from where you are running your Ansible play. For example:

Delete a file if it already exists on Ansible host:

 - name: Remove file if already exists
    path: /tmp/logfile.log
    state: absent
    mode: "u+rw,g-wx,o-rwx"

Create a new file on Ansible host :

 - name: Create log file
    path: /tmp/logfile.log
    state: touch
    mode: "u+rw,g-wx,o-rwx"

How to get current time in python and break up into year, month, day, hour, minute?

Let's see how to get and print day,month,year in python from current time:

import datetime

now =
year = '{:02d}'.format(now.year)
month = '{:02d}'.format(now.month)
day = '{:02d}'.format(
hour = '{:02d}'.format(now.hour)
minute = '{:02d}'.format(now.minute)
day_month_year = '{}-{}-{}'.format(year, month, day)

print('day_month_year: ' + day_month_year)


day_month_year: 2019-03-26

Make body have 100% of the browser height

You can also use JS if needed

var winHeight = window.innerHeight    || 
document.documentElement.clientHeight || 

var pageHeight = $('body').height();
if (pageHeight < winHeight) {

How do I ignore a directory with SVN?

Remove it first...

If your directory foo is already under version control, remove it first with:

svn rm --keep-local foo

...then ignore:

svn propset svn:ignore foo .

Embedding VLC plugin on HTML page

I found this piece of code somewhere in the web. Maybe it helps you and I give you an update so far I accomodated it for the same purpose... Maybe I don't.... who the futt knows... with all the nogodders and dobedders in here :-/

function runVLC(target, stream)
var support=true
var addr='rtsp://' + window.location.hostname + stream
if ($.browser.msie){
$(target).html('<object type = "application/x-vlc-plugin"' + 'version =  
"VideoLAN.VLCPlugin.2"' + 'classid = "clsid:9BE31822-FDAD-461B-AD51-BE1D1C159921"' + 
'events = "true"' + 'id = "vlc"></object>')
else if ($.browser.mozilla || $.browser.webkit){
$(target).html('<embed type = "application/x-vlc-plugin"' + 'class="vlc_plugin"' + 
'pluginspage=""' + 'version="VideoLAN.VLCPlugin.2" ' + 
'width="660" height="372"' + 
'id="vlc"' + 'autoplay="true"' + 'allowfullscreen="false"' + 'windowless="true"' + 
'mute="false"' + 'loop="true"' + '<toolbar="false"' + 'bgcolor="#111111"' + 
'branding="false"' + 'controls="false"' + 'aspectRatio="16:9"' + 
$(target).empty().html('<div id = "dialog_error">Error: browser not supported!</div>')
if (support){
var vlc = document.getElementById('vlc')
if (vlc){
var opt = new Array(':network-caching=300')
var id = vlc.playlist.add(addr, '', opt)
catch (e){
$(target).empty().html('<div id = "dialog_error">Error: ' + e + '<br>URL: ' + addr + 
/* $(target + ' object').css({'width': '100%', 'height': '100%'}) */



I reduce the whole crap now to:

function runvlc(){
var target=$('body')
var error=$('#dialog_error')
var support=true
var addr='rtsp://../html/media/video/TESTCARD.MP4'
if (navigator.userAgent.toLowerCase().indexOf("msie")!=-1){
target.append('<object type = "application/x-vlc-plugin"' + 'version = "
VideoLAN.VLCPlugin.2"' + 'classid = "clsid:9BE31822-FDAD-461B-AD51-BE1D1C159921"' + 
'events = "true"' + 'id = "vlc"></object>')
else if (navigator.userAgent.toLowerCase().indexOf("msie")==-1){
target.append('<embed type = "application/x-vlc-plugin"' + 'class="vlc_plugin"' + 
'pluginspage=""' + 'version="VideoLAN.VLCPlugin.2" ' + 
'width="660" height="372"' + 
'id="vlc"' + 'autoplay="true"' + 'allowfullscreen="false"' + 'windowless="true"' + 
'mute="false"' + 'loop="true"' + '<toolbar="false"' + 'bgcolor="#111111"' + 
'branding="false"' + 
'controls="false"' + 'aspectRatio="16:9"' + 'target="whatever.mp4">
error.empty().html('Error: browser not supported!')
if (support){
var vlc=document.getElementById('vlc')
if (vlc){
var options=new Array(':network-caching=300') /* set additional vlc--options */
try{ /* error handling */
var id = vlc.playlist.add(addr,'',options)
catch (e){
error.empty().html('Error: ' + e + '<br>URL: ' + addr + '')

Didn't get it to work in ie as well... 2b continued...



Embedding DLLs in a compiled executable

I highly recommend to use Costura.Fody - by far the best and easiest way to embed resources in your assembly. It's available as NuGet package.

Install-Package Costura.Fody

After adding it to the project, it will automatically embed all references that are copied to the output directory into your main assembly. You might want to clean the embedded files by adding a target to your project:


You'll also be able to specify whether to include the pdb's, exclude certain assemblies, or extracting the assemblies on the fly. As far as I know, also unmanaged assemblies are supported.


Currently, some people are trying to add support for DNX.

Update 2

For the lastest Fody version, you will need to have MSBuild 16 (so Visual Studio 2019). Fody version 4.2.1 will do MSBuild 15. (reference: Fody is only supported on MSBuild 16 and above. Current version: 15)